ALTER DATABASE modifies a database, including its name, owner, connection limitation, and object isolation.
+
+
Precautions
+
Only the owner of a database or a system administrator has the permission to run the ALTER DATABASE statement. Users other than system administrators may have the following permission constraints depending on the attributes to be modified:
To modify the database name, you must have the CREATEDB permission.
To modify a database owner, you must be a database owner and a member of the new owner, and have the CREATEDB permission.
To change the default tablespace, you must be a database owner or a system administrator, and must have the CREATE permission on the new tablespace. This statement physically migrates tables and indexes in a default tablespace to a new tablespace. Note that tables and indexes outside the default tablespace are not affected.
Only a database owner or a system administrator can modify GUC parameters for the database.
Only database owners and system administrators can modify the object isolation attribute of a database.
+
You are not allowed to rename a database in use. To rename it, connect to another database.
+
+
Examples
+
-- Set the maximum number of connections to database music to 10:
+postgres=# ALTER DATABASE music CONNECTION LIMIT= 10 ;
+
+-- Rename database music to music4:
+postgres=# ALTER DATABASE music RENAME TO music4 ;
+
+-- Change the owner of database music2 to user tom:
+postgres=# ALTER DATABASE music2 OWNER TO tom ;
+
+-- Set the tablespace of database music3 to PG_DEFAULT:
+postgres=# ALTER DATABASE music3 SET TABLESPACE PG_DEFAULT ;
+
+-- Disable the default index scan on database music3.
+postgres=# ALTER DATABASE music3 SET enable_indexscan TO off ;
+
+-- Reset the enable_indexscan parameter.
+postgres=# ALTER DATABASE music3 RESET enable_indexscan ;
+Delete the databases:
+postgres=# DROP DATABASE music2 ;
+postgres=# DROP DATABASE music3 ;
+postgres=# DROP DATABASE music4 ;
+
+
Syntax
+
Modify the maximum number of connections to the database.
ALTER DATABASE database_name
+ [ [ WITH ] CONNECTION LIMIT connlimit ];
+
Rename the database.
ALTER DATABASE database_name
+ RENAME TO new_name;
+
Change the database owner.
ALTER DATABASE database_name
+ OWNER TO new_owner;
+
Change the default tablespace of the database.
ALTER DATABASE database_name
+ SET TABLESPACE new_tablespace;
+
Modify the session parameter value of the database.
ALTER DATABASE database_name
+ SET configuration_parameter { { TO | = } { value | DEFAULT } | FROM CURRENT };
+
Reset the database configuration parameter.
ALTER DATABASE database_name RESET
+ { configuration_parameter | ALL };
+
+
+
Parameter Description
+
+
database_name
+
Specifies the name of the database whose attributes are to be modified.
+
Value range: a string. It must comply with the naming convention rule.
+
+
connlimit
+
Specifies the maximum number of concurrent connections that can be made to this database (excluding administrators' connections).
+
Value range: The value must be an integer, preferably from 1 to 50. The default value -1 indicates that there is no restriction on the number of concurrent connections.
+
+
new_name
+
Specifies the new name of a database.
+
Value range: a string. It must comply with the naming convention rule.
+
+
new_owner
+
Specifies the new owner of a database.
+
Value range: a string. It must be a valid username.
+
+
new_tablespace
+
Specifies the new default tablespace of a database. The tablespace exists in the database. The default tablespace is pg_default.
+
Value range: a string. It must be a valid tablespace name.
+
+
configuration_parameter
+
value
+
Sets a specified database session parameter to a specified value. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.
+
Value range: a string
+
DEFAULT
OFF
RESET
+
+
FROM CURRENT
+
Sets the value of the database based on the current connected session.
+
+
RESET configuration_parameter
+
Resets the specified database session parameter.
+
+
RESET ALL
+
Resets all database session parameters.
+
]]>
+
+
+
Function
+
ALTER DATA SOURCE modifies the attributes and content of the data source.
+
The attributes include the name and owner. The content includes the type, version, and connection options.
+
+
Precautions
+
Only the initial user, system administrator, and owner have the permission to modify data sources.
To change the owner, the new owner must be the initial user or a system administrator.
If the password option is displayed, ensure that the datasource.key.cipher and datasource.key.rand files exist in the $GAUSSHOME/bin directory of each node in openGauss. If the two files do not exist, use the gs_guc tool to generate them and use the gs_ssh tool to release them to the $GAUSSHOME/bin directory on each node in openGauss.
+
+
Examples
+
-- Rename the data source.
+postgres=# ALTER DATA SOURCE ds_test1 RENAME TO ds_test;
+
+-- Change the owner.
+postgres=# CREATE USER user_test1 IDENTIFIED BY ' Gs@123456 ' ;
+postgres=# ALTER USER user_test1 WITH SYSADMIN ;
+postgres=# ALTER DATA SOURCE ds_test OWNER TO user_test1 ;
+
+-- Modify TYPE and VERSION.
+postgres=# ALTER DATA SOURCE ds_test TYPE ' MPPDB_TYPE ' VERSION ' XXX ' ;
+
+-- Add a column.
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( add dsn ' gaussdb ' , username ' test_user ' ) ;
+
+-- Modify a column.
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( set dsn ' unknown ' ) ;
+
+-- Delete a column.
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( drop username ) ;
+
+
Syntax
+
ALTER DATA SOURCE src_name
+ [TYPE 'type_str']
+ [VERSION {'version_str' | NULL}]
+ [OPTIONS ( {[ ADD | SET | DROP ] optname ['optvalue']} [, ...] )];
+ALTER DATA SOURCE src_name RENAME TO src_new_name;
+ALTER DATA SOURCE src_name OWNER TO new_owner;
+
+
Parameter Description
+
+
src_name
+
Specifies the data source name to be modified.
+
Value range: a string. It must comply with the naming convention rule.
+
+
TYPE
+
Changes the original TYPE value of the data source to the specified value.
+
Value range: an empty string or a non-empty string
+
+
VERSION
+
Changes the original VERSION value of the data source to the specified value.
+
Value range: an empty string, a non-empty string, or null
+
+
OPTIONS
+
Specifies the column to be added, modified, or deleted. The value of optname should be unique. Comply with the following rules to set this parameter:
+
To add a column, you can omit ADD and simply specify the column name, which cannot be an existing column name.
+
To modify a column, specify SET and an existing column name.
+
To delete a column, specify DROP and an existing column name. Do not set optvalue.
+
+
src_new_name
+
Specifies the new data source name.
+
Value range: a string. It must comply with the naming convention rule.
+
+
new_user
+
Specifies the new owner of an object.
+
Value range: a string. It must be a valid username.
+
]]>
+
+
+
Function
+
ALTER DEFAULT PRIVILEGES allows you to set the permissions that will be applied to objects created in the future. (It does not affect permissions granted to existing objects.)
+
+
Precautions
+
Only the permissions for tables (including views), functions, and types (including domains) can be altered.
+
+
Syntax
+
ALTER DEFAULT PRIVILEGES
+ [ FOR { ROLE | USER } target_role [, ...] ]
+ [ IN SCHEMA schema_name [, ...] ]
+ abbreviated_grant_or_revoke;
+
abbreviated_grant_or_revoke grants or revokes permissions on some objects.
grant_on_tables_clause grants permissions on tables.
GRANT { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES }
+ [, ...] | ALL [ PRIVILEGES ] }
+ ON TABLES
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ]
+
grant_on_functions_clause grants permissions on functions.
GRANT { EXECUTE | ALL [ PRIVILEGES ] }
+ ON FUNCTIONS
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ]
+
grant_on_types_clause grants permissions on types.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON TYPES
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ]
+
revoke_on_tables_clause revokes permissions on tables.
REVOKE [ GRANT OPTION FOR ]
+ { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES }
+ [, ...] | ALL [ PRIVILEGES ] }
+ ON TABLES
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT | CASCADE CONSTRAINTS ]
+
revoke_on_functions_clause revokes permissions on functions.
REVOKE [ GRANT OPTION FOR ]
+ { EXECUTE | ALL [ PRIVILEGES ] }
+ ON FUNCTIONS
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT | CASCADE CONSTRAINTS ]
+
revoke_on_types_clause revokes permissions on types.
REVOKE [ GRANT OPTION FOR ]
+ { USAGE | ALL [ PRIVILEGES ] }
+ ON TYPES
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT | CASCADE CONSTRAINTS ]
+
+
+
Parameter Description
+
+
target_role
+
Specifies the name of an existing role. If FOR ROLE/USER is omitted, the current role is assumed.
+
Value range: an existing role name
+
+
schema_name
+
Specifies the name of an existing schema.
+
target_role must have the CREATE permission for schema_name.
+
Value range: an existing schema name
+
+
role_name
+
Specifies the name of an existing role to grant or revoke permissions for.
+
Value range: an existing role name
+
]]>
+
+
+
Function
+
ALTER DIRECTORY modifies a directory.
+
+
Precautions
+
Currently, only the directory owner can be changed.
The owner can only be a user with the sysadmin permission.
+
+
Examples
+
-- Change the owner of the directory.
+postgres=# ALTER DIRECTORY dir OWNER TO system ;
+
+
Syntax
+
ALTER DIRECTORY directory_name
+ OWNER TO new_owner;
+
+
Parameter Description
+
directory_name
+
Specifies the name of a directory to be modified. The value must be an existing directory name.
+
]]>
+
+
+
Function
+
ALTER FUNCTION modifies the attributes of a customized function.
+
+
Precautions
+
Only the owner of the function or a system administrator has the permission to run this statement. If a function involves operations on temporary tables, ALTER FUNCTION cannot be used.
+
+
Examples
+
-- Alter the execution rule of function add to IMMUTABLE ( that is, the same result is returned if the parameter remains unchanged ) .
+postgres=# ALTER FUNCTION func_add_sql2 ( INTEGER , INTEGER ) IMMUTABLE ;
+
+-- Alter the name of function add to add_two_number.
+postgres=# ALTER FUNCTION func_add_sql2 ( INTEGER , INTEGER ) RENAME TO add_two_number ;
+
+-- Change the owner of function add to omm.
+postgres=# ALTER FUNCTION add_two_number ( INTEGER , INTEGER ) OWNER TO omm ;
+
+
Syntax
+
Modify the additional parameters of the customized function.
ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
+ RENAME TO new_name;
+
Change the owner of the customized function.
ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
+ OWNER TO new_owner;
+
Modify the schema of the customized function.
ALTER FUNCTION funname ( [ { [ argmode ] [ argname ] argtype} [, ...] ] )
+ SET SCHEMA new_schema;
+
+
+
Parameter Description
+
+
function_name
+
Specifies the name of the function to be modified.
+
Value range: an existing function name
+
+
argmode
+
Specifies whether a parameter is an input or output parameter.
+
Value range: IN, OUT, and IN OUT
+
+
argname
+
Parameter name.
+
Value range: a string. It must comply with the naming convention rule.
+
+
argtype
+
Parameter type.
+
Value range: a valid type. For details, see Data Types.
+
+
CALLED ON NULL INPUT
+
Declares that some parameters of the function can be invoked in normal mode if the parameter values are null. Omitting this parameter is the same as specifying it.
+
+
RETURNS NULL ON NULL INPUT
+
STRICT
+
Specifies that the function always returns null whenever any of its parameters is null. If STRICT is specified, the function will not be executed when there are null parameters; instead a null result is assumed automatically.
+
RETURNS NULL ON NULL INPUT and STRICT have the same functions.
+
+
IMMUTABLE
+
Specifies that the function always returns the same result if the parameter values are the same.
+
+
STABLE
+
Specifies that the function cannot modify the database, and that within a single table scan it will consistently return the same result for the same parameter value, but its result varies by SQL statements.
+
+
VOLATILE
+
Specifies that the function value can change in a single table scan and no optimization is performed.
+
+
LEAKPROOF
+
Specifies that the function has no side effect and the parameter contains only the return value. LEAKROOF can be set only by a system administrator.
+
+
EXTERNAL
+
(Optional) The purpose is to be compatible with SQL. This feature applies to all functions, not only external functions.
+
+
SECURITY INVOKER
+
AUTHID CURREN_USER
+
Specifies that the function will be executed with the permissions of the user who invokes it. Omitting this parameter is the same as specifying it.
+
SECURITY INVOKER and AUTHID CURRENT_USER have the same functions.
+
+
SECURITY DEFINER
+
AUTHID DEFINER
+
Specifies that the function will be executed with the permissions of the user who created it.
+
AUTHID DEFINER and SECURITY DEFINER have the same function.
+
+
COST execution_cost
+
Estimates the execution cost of a function.
+
The unit of execution_cost is cpu_operator_cost.
+
Value range: a positive integer
+
+
ROWS result_rows
+
Estimates the number of rows returned by the function. This is only allowed when the function is declared to return a set.
+
Value range: a positive number. The default value is 1000.
+
+
configuration_parameter
+
value
Sets a specified database session parameter to a specified value. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.
+
Value range: a string
+
DEFAULT
OFF
RESET
+
Specifies the default value.
+
from current
Uses the value of configuration_parameter of the current session.
+
+
+
new_name
+
Specifies the new name of a function. To change the schema of a function, you must have the CREATE permission on the new schema.
+
Value range: a string. It must comply with the naming convention rule.
+
+
new_owner
+
Specifies the new owner of a function. To change the owner of a function, the new owner must have the CREATE permission on the schema to which the function belongs.
+
Value range: an existing user role
+
+
new_schema
+
Specifies the new schema of a function.
+
Value range: an existing schema
+
]]>
+
+
+
Function
+
ALTER GROUP modifies the attributes of a user group.
+
+
Precautions
+
ALTER GROUP is an alias for ALTER ROLE, and it is not a standard SQL syntax and not recommended. Users can use ALTER ROLE directly.
+
+
Syntax
+
Add users to a group.
ALTER GROUP group_name
+ ADD USER user_name [, ... ];
+
+
Remove users from a group.
ALTER GROUP group_name
+ DROP USER user_name [, ... ];
ALTER INDEX modifies the definition of an existing index.
+
It has the following forms:
+
IF EXISTS
Sends a notice instead of an error if the specified index does not exist.
+
RENAME TO
Changes only the name of the index. The stored data is not affected.
+
SET TABLESPACE
This option changes the index tablespace to the specified tablespace and moves index-related data files to the new tablespace.
+
SET ( { STORAGE_PARAMETER = value } [, ...] )
Changes one or more index-method-specific storage parameters of an index. Note that the index content will not be modified immediately by this statement. You may need to use REINDEX to recreate the index based on different parameters to achieve the expected effect.
+
RESET ( { storage_parameter } [, ...] )
Resets one or more index-method-specific storage parameters of an index to the default value. Similar to the SET statement, REINDEX may be used to completely update the index.
Sets the indexes on a table or index partition to be unavailable.
+
REBUILD [ PARTITION index_partition_name ]
Rebuilds indexes on a table or an index partition.
+
RENAME PARTITION
Renames an index partition.
+
MOVE PARTITION
Modifies the tablespace to which an index partition belongs.
+
+
+
Precautions
+
Only the index owner or a system administrator can run this statement.
+
+
Examples
+
-- Rename an existing index.
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index1 RENAME TO ds_ship_mode_t1_index5 ;
+
+-- Set the index as unusable.
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index2 UNUSABLE ;
+
+-- Rebuild an index.
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index2 REBUILD ;
+
+-- Change the tablespace of the partitioned table index CA_ADDRESS_SK_index2 to example1.
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 MOVE PARTITION CA_ADDRESS_SK_index2 TABLESPACE example1 ;
+
+-- Change the tablespace of the partitioned table index CA_ADDRESS_SK_index3 to example2.
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 MOVE PARTITION CA_ADDRESS_SK_index3 TABLESPACE example2 ;
+
+-- Rename a partitioned table index.
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 RENAME PARTITION CA_ADDRESS_SK_index1 TO CA_ADDRESS_SK_index4 ;
+
+
Syntax
+
Rename a table index.
ALTER INDEX [ IF EXISTS ] index_name
+ RENAME TO new_name;
+
+
Change the tablespace to which a table index belongs.
ALTER INDEX [ IF EXISTS ] index_name
+ SET TABLESPACE tablespace_name;
+
+
Modify the storage parameter of a table index.
ALTER INDEX [ IF EXISTS ] index_name
+ SET ( {storage_parameter = value} [, ... ] );
+
+
Reset the storage parameter of a table index.
ALTER INDEX [ IF EXISTS ] index_name
+ RESET ( storage_parameter [, ... ] ) ;
+
+
Set a table index or an index partition to be unavailable.
ALTER INDEX [ IF EXISTS ] index_name
+ [ MODIFY PARTITION index_partition_name ] UNUSABLE;
+
The syntax cannot be used for column-store tables.
+
+
+
Rebuild a table index or index partition.
ALTER INDEX index_name
+ REBUILD [ PARTITION index_partition_name ];
+
+
Rename an index partition.
ALTER INDEX [ IF EXISTS ] index_name
+ RENAME PARTITION index_partition_name TO new_index_partition_name;
+
+
Modify the tablespace to which an index partition belongs.
ALTER INDEX [ IF EXISTS ] index_name
+ MOVE PARTITION index_partition_name TABLESPACE new_tablespace;
+
+
+
Parameter Description
+
+
index_name
+
Specifies the index name to be modified.
+
+
new_name
+
Specifies the new name of the index.
+
Value range: a string. It must comply with the naming convention rule.
+
+
tablespace_name
+
Specifies the tablespace name.
+
Value range: an existing tablespace name
+
+
storage_parameter
+
Specifies the name of an index-method-specific parameter.
+
+
value
+
Specifies the new value for an index-method-specific storage parameter. This might be a number or a word depending on the parameter.
+
+
new_index_partition_name
+
Specifies the new name of the index partition.
+
+
index_partition_name
+
Specifies the name of an index partition.
+
+
new_tablespace
+
Specifies a new tablespace.
+
]]>
+
+
+
Function
+
ALTER LARGE OBJECT changes the owner of a large object.
+
+
Precautions
+
Only a system administrator or the owner of the to-be-modified large object can run ALTER LARGE OBJECT.
+
+
Syntax
+
ALTER LARGE OBJECT large_object_oid
+ OWNER TO new_owner;
+
+
Parameter Description
+
+
large_object_oid
+
Specifies the OID of the large object to be modified.
+
Value range: an existing large object name
+
+
OWNER TO new_owner
+
Specifies the new owner of an object.
+
Value range: an existing username or role name
+
]]>
+
+
+
Function
+
ALTER ROLE modifies role attributes.
+
+
Syntax
+
Modify the permissions of a role.
ALTER ROLE role_name [ [ WITH ] option [ ... ] ];
+
The option clause for granting permissions is as follows:
ALTER ROLE role_name [ IN DATABASE database_name ]
+ SET configuration_parameter {{ TO | = } { value | DEFAULT } | FROM CURRENT};
+
Reset parameters for a role.
ALTER ROLE role_name
+ [ IN DATABASE database_name ] RESET {configuration_parameter|ALL};
+
+
+
Parameter Description
+
+
role_name
+
Specifies a role name.
+
Value range: an existing username
+
+
IN DATABASE database_name
+
Modifies the parameters of a role in a specified database.
+
+
SET configuration_parameter
+
Sets parameters for a role. Session parameters modified by ALTER ROLE apply to a specified role and take effect in the next session triggered by the role.
+
Value range:
+
For details about the values of configuration_parameter and value, see SET.
+
DEFAULT: clears the value of configuration_parameter. configuration_parameter will inherit the default value of the new session generated for the role.
+
FROM CURRENT: uses the value of configuration_parameter of the current session.
+
+
RESET configuration_parameter/ALL
+
Clears the value of configuration_parameter. The statement has the same effect as that of SET configuration_parameter TO DEFAULT.
+
Value range: ALL indicates that the values of all parameters are cleared.
+
+
ACCOUNT LOCK | ACCOUNT UNLOCK
+
ACCOUNT LOCK: locks an account to forbid login to databases.
ACCOUNT UNLOCK: unlocks an account to allow login to databases.
+
+
PGUSER
+
In the current version, the PGUSER attribute of a role cannot be modified.
+
]]>
+
+
+
Function
+
ALTER ROW LEVEL SECURITY POLICY modifies an existing row-level access control policy, including the policy name and the users and expressions affected by the policy.
+
+
Precautions
+
Only the table owner or a system administrator can perform this operation.
+
+
Examples
+
-- Change the name of the all_data_rls policy.
+postgres=# ALTER ROW LEVEL SECURITY POLICY all_data_rls ON all_data RENAME TO all_data_new_rls ;
+
+-- Change the users affected by the row-level access control policy.
+postgres=# ALTER ROW LEVEL SECURITY POLICY all_data_new_rls ON all_data TO alice , bob ;
+postgres=# \d+ all_data
+Table "public.all_data"
+Column | Type | Modifiers | Storage | Stats target | Description
+--------+------------------------+-----------+----------+--------------+-------------
+id | integer | | plain | |
+role | character varying ( 100 ) | | extended | |
+data | character varying ( 100 ) | | extended | |
+Row Level Security Policies:
+POLICY "all_data_new_rls"
+TO alice , bob
+USING ( ( ( role ) ::name = "current_user" ( ) ) )
+Has OIDs: no
+Location Nodes: ALL DATANODES
+Options: orientation=row , compression=no , enable_rowsecurity=true
+
+-- Modify the expression defined for the access control policy.
+postgres=# ALTER ROW LEVEL SECURITY POLICY all_data_new_rls ON all_data USING ( id > 100 AND role = current_user ) ;
+postgres=# \d+ all_data
+Table "public.all_data"
+Column | Type | Modifiers | Storage | Stats target | Description
+--------+------------------------+-----------+----------+--------------+-------------
+id | integer | | plain | |
+role | character varying ( 100 ) | | extended | |
+data | character varying ( 100 ) | | extended | |
+Row Level Security Policies:
+POLICY "all_data_new_rls"
+TO alice , bob
+USING ( ( ( id > 100 ) AND ( ( role ) ::name = "current_user" ( ) ) ) )
+Has OIDs: no
+Location Nodes: ALL DATANODES
+Options: orientation=row , compression=no , enable_rowsecurity=true
+
+
Syntax
+
ALTER [ ROW LEVEL SECURITY ] POLICY [ IF EXISTS ] policy_name ON table_name RENAME TO new_policy_name;
+
+ALTER [ ROW LEVEL SECURITY ] POLICY policy_name ON table_name
+ [ TO { role_name | PUBLIC } [, ...] ]
+ [ USING ( using_expression ) ];
+
+
Parameter Description
+
+
policy_name
+
Specifies the name of a row-level access control policy.
+
+
table_name
+
Specifies the name of a table to which a row-level access control policy is applied.
+
+
new_policy_name
+
Specifies the new name of a row-level access control policy.
+
+
role_name
+
Specifies names of users affected by a row-level access control policy. PUBLIC indicates that the row-level access control policy will affect all users.
+
+
using_expression
+
Specifies an expression defined for a row-level access control policy. The return value is of the boolean type.
+
]]>
+
+
+
Function
+
ALTER SCHEMA modifies schema properties.
+
+
Precautions
+
Only the owner of a schema or a system administrator has the permission to run the ALTER SCHEMA statement.
+
+
Examples
+
-- Rename the current schema ds to ds_new.
+postgres=# ALTER SCHEMA ds RENAME TO ds_new ;
+
+-- Change the owner of ds_new to jack.
+postgres=# ALTER SCHEMA ds_new OWNER TO jack ;
+
+
Syntax
+
Rename a schema.
ALTER SCHEMA schema_name
+ RENAME TO new_name;
+
Change the owner of a schema.
ALTER SCHEMA schema_name
+ OWNER TO new_owner;
+
+
+
Parameter Description
+
+
schema_name
+
Specifies the name of an existing schema.
+
Value range: an existing schema name
+
+
RENAME TO new_name
+
Renames a schema.
+
new_name: new name of the schema.
+
Value range: a string. It must comply with the naming convention rule.
+
+
OWNER TO new_owner
+
Changes the owner of a schema. To do this as a non-administrator, you must be a direct or indirect member of the new owning role, and that role must have CREATE permission in the database.
+
new_owner: new owner of the schema.
+
Value range: an existing username or role name
+
]]>
+
+
+
Function
+
ALTER SEQUENCE modifies the parameters of an existing sequence.
+
+
Precautions
+
You must be the owner of the sequence to use ALTER SEQUENCE.
In the current version, you can modify only the owner, owning column, and maximum value. To modify other parameters, delete the sequence and create it again. Then, use the Setval function to restore parameter values.
ALTER SEQUENCE MAXVALUE cannot be used in transactions, functions, and stored procedures.
After the maximum value of a sequence is changed, the cache of the sequence in all sessions is cleared.
The ALTER SEQUENCE statement blocks the invoking of nextval, setval, currval, and lastval.
+
+
Examples
+
-- Change the owning column of serial to T1.C1.
+postgres=# ALTER SEQUENCE serial OWNED BY T1.C1 ;
+
+
Syntax
+
Change the owning column of a sequence.
+
ALTER SEQUENCE [ IF EXISTS ] name
+ [MAXVALUE maxvalue | NO MAXVALUE | NOMAXVALUE]
+ [ OWNED BY { table_name.column_name | NONE } ] ;
+
Change the owner of a sequence.
+
ALTER SEQUENCE [ IF EXISTS ] name OWNER TO new_owner;
+
+
Parameter Description
+
+
name
+
Specifies the name of the sequence to be modified.
+
+
IF EXISTS
+
Sends a notice instead of an error when you are modifying a nonexisting sequence.
+
+
OWNED BY
+
Associates a sequence with a specified column included in a table. In this way, the sequence will be deleted when you delete its associated column or the table where the column belongs to.
+
If the sequence has been associated with another table before you use this option, the new association will overwrite the old one.
+
The associated table and sequence must be owned by the same user and in the same schema.
+
If OWNED BY NONE is used, all existing associations will be deleted.
+
+
new_owner
+
Specifies the username of the new owner of the sequence. To change the owner, you must also be a direct or indirect member of the new role, and this role must have CREATE permission on the sequence's schema.
+
]]>
+
+
+
Function
+
ALTER SESSION defines or modifies the conditions or parameters that affect the current session. Modified session parameters are kept until the current session is disconnected.
+
+
Precautions
+
If the START TRANSACTION statement is not executed before the SET TRANSACTION statement, the transaction is ended instantly and the statement does not take effect.
You can use the transaction_mode(s) method declared in the START TRANSACTION statement to avoid using the SET TRANSACTION statement.
+
+
Examples
+
-- Set the character code of the current session to UTF8.
+postgres=# ALTER SESSION SET NAMES ' UTF8 ' ;
+
+-- Set the current schema.
+postgres=# ALTER SESSION SET CURRENT_SCHEMA TO tpcds ;
+
+-- Set XML OPTION to DOCUMENT.
+postgres=# ALTER SESSION SET XML OPTION DOCUMENT ;
+
+-- Create the role joe and set it as the session role.
+postgres=# CREATE ROLE joe WITH PASSWORD ' Bigdata@123 ' ;
+postgres=# ALTER SESSION SET SESSION AUTHORIZATION joe PASSWORD ' Bigdata@123 ' ;
+
+-- Switch to the default user.
+postgres=> ALTER SESSION SET SESSION AUTHORIZATION default;
+
+
Syntax
+
Set transaction parameters of a session.
ALTER SESSION SET [ SESSION CHARACTERISTICS AS ] TRANSACTION
+ { ISOLATION LEVEL { READ COMMITTED } | { READ ONLY | READ WRITE } } [, ...] ;
+
Set other running parameters of a session.
ALTER SESSION SET
+ {{config_parameter { { TO | = } { value | DEFAULT }
+ | FROM CURRENT }}
+ | TIME ZONE time_zone
+ | CURRENT_SCHEMA schema
+ | NAMES encoding_name
+ | ROLE role_name PASSWORD 'password'
+ | SESSION AUTHORIZATION { role_name PASSWORD 'password' | DEFAULT }
+ | XML OPTION { DOCUMENT | CONTENT }
+ } ;
+
+
+
Parameter Description
+
For details about the descriptions of parameters related to ALTER SESSION, see Parameter Description of the SET syntax.
+
]]>
+
+
+
Function
+
ALTER SYNONYM modifies the attributes of the SYNONYM object.
+
+
Precautions
+
Currently, only the owner of the SYNONYM object can be changed.
Only the system administrator has the permission to modify the owner of the SYNONYM object.
The new owner must have the CREATE permission on the schema where the SYNONYM object resides.
+
+
Examples
+
-- Change the owner of synonym t1 to u1.
+postgres=# ALTER SYNONYM t1 OWNER TO u1 ;
+
+
Syntax
+
ALTER SYNONYM synonym_name
+ OWNER TO new_owner;
+
+
Parameter Description
+
+
synonym
+
Specifies the name of the synonym to be modified, which can contain the schema name.
+
Value range: a string. It must comply with the naming convention rule.
+
]]>
+
+
+
Function
+
ALTER SYSTEM KILL SESSION ends a session.
+
+
Syntax
+
ALTER SYSTEM KILL SESSION 'session_sid, serial' [ IMMEDIATE ];
+
+
Parameter Description
+
+
session_sid, serial
+
Specifies the SID and SERIAL of a session (To obtain the values, see the example.)
+
+
+
IMMEDIATE
+
Specifies that a session will be ended instantly after the statement is executed.
+
]]>
+
+
+
Function
+
ALTER TABLE modifies tables, including modifying table definitions, renaming tables, renaming specified columns in tables, renaming table constraints, setting table schemas, enabling or disabling row-level access control, and adding or updating multiple columns.
+
+
Precautions
+
Only the table owner or a system administrator has the permission to run the ALTER TABLE statement.
The tablespace of a partitioned table cannot be modified, but the tablespace of the partition can be modified.
The storage parameter ORIENTATION cannot be modified.
Currently, SET SCHEMA can only set schemas to user schemas. It cannot set a schema to a system internal schema.
Column-store tables support only PARTIAL CLUSTER KEY table-level constraints, but do not support primary and foreign key table-level constraints.
In a column-store table, you can perform ADD COLUMN, ALTER TYPE, SET STATISTICS, DROP COLUMN operations, and change table name and space. The types of new and modified columns should be the Data Types supported by column-store. The USING option of ALTER TYPE only supports constant expression and expression involved in the column.
The column constraints supported by column-store tables include NULL, NOT NULL, and DEFAULT constant values. Only the DEFAULT value can be modified (by using SET DEFAULT and DROP DEFAULT). Currently, NULL and NOT NULL constraints cannot be modified.
+
+
Syntax
+
Modify the definition of a table.
ALTER TABLE [ IF EXISTS ] { table_name [*] | ONLY table_name | ONLY ( table_name ) }
+ action [, ... ];
+
There are several clauses of action:
column_clause
+ | ADD table_constraint [ NOT VALID ]
+ | ADD table_constraint_using_index
+ | VALIDATE CONSTRAINT constraint_name
+ | DROP CONSTRAINT [ IF EXISTS ] constraint_name [ RESTRICT | CASCADE ]
+ | CLUSTER ON index_name
+ | SET WITHOUT CLUSTER
+ | SET ( {storage_parameter = value} [, ... ] )
+ | RESET ( storage_parameter [, ... ] )
+ | OWNER TO new_owner
+ | SET TABLESPACE new_tablespace
+ | SET {COMPRESS|NOCOMPRESS}
+ | TO { GROUP groupname | NODE ( nodename [, ... ] ) }
+ | ADD NODE ( nodename [, ... ] )
+ | DELETE NODE ( nodename [, ... ] )
+ | DISABLE TRIGGER [ trigger_name | ALL | USER ]
+ | ENABLE TRIGGER [ trigger_name | ALL | USER ]
+ | ENABLE REPLICA TRIGGER trigger_name
+ | ENABLE ALWAYS TRIGGER trigger_name
+ | DISABLE ROW LEVEL SECURITY
+ | ENABLE ROW LEVEL SECURITY
+ | FORCE ROW LEVEL SECURITY
+ | NO FORCE ROW LEVEL SECURITY
+
ADD table_constraint [ NOT VALID ]
Adds a table constraint.
+
ADD table_constraint_using_index
Adds a primary key constraint or unique constraint to a table based on the existing unique index.
+
VALIDATE CONSTRAINT constraint_name
Validates a check-class constraint created with the NOT VALID option, and scans the entire table to ensure that all rows meet the constraint. Nothing happens if the constraint is already marked valid.
+
DROP CONSTRAINT [ IF EXISTS ] constraint_name [ RESTRICT | CASCADE ]
Drops a table constraint.
+
CLUSTER ON index_name
Selects the default index for future CLUSTER operations. Actually, the table is not re-clustered.
+
SET WITHOUT CLUSTER
Deletes the most recently used CLUSTER index from the table. This affects future CLUSTER operations that do not specify an index.
+
SET ( {storage_parameter = value} [, ... ] )
Changes one or more storage parameters for the table.
+
RESET ( storage_parameter [, ... ] )
Resets one or more storage parameters to their defaults. As with SET, a table rewrite might be needed to update the table entirely.
+
OWNER TO new_owner
Changes the owner of a table, sequence, or view to the specified user.
+
SET TABLESPACE new_tablespace
Changes the table's tablespace to the specified tablespace and moves the data files associated with the table to the new tablespace. Indexes on the table, if any, are not moved; but they can be moved separately with additional SET TABLESPACE option in ALTER INDEX.
+
SET {COMPRESS|NOCOMPRESS}
Sets the compression feature of a table. The table compression feature affects only the storage mode of data inserted in a batch subsequently and does not affect storage of existing data. Setting the table compression feature will result in the fact that there are both compressed and uncompressed data in the table.
+
TO { GROUP groupname | NODE ( nodename [, ... ] ) }
The syntax is only available in extended mode (when GUC parameter support_extended_features is on). Exercise caution when enabling the mode. It is mainly used for tools like internal scale-out tools. Common users should not use the mode.
+
ADD NODE ( nodename [, ... ] )
It is only available for internal scale-out tools. Common users should not use the syntax.
+
DELETE NODE ( nodename [, ... ] )
It is only available for internal scale-in tools. Common users should not use the syntax.
+
DISABLE TRIGGER [ trigger_name | ALL | USER ]
Disables a single trigger specified by trigger_name, disables all triggers, or disables only user triggers (excluding internally generated constraint triggers, for example, deferrable unique constraint triggers and exclusion constraint triggers).
+
Exercise caution when using this function because data integrity cannot be ensured as expected if the triggers are not executed.
+
+
| ENABLE TRIGGER [ trigger_name | ALL | USER ]
Enables a single trigger specified by trigger_name, enables all triggers, or enables only user triggers.
+
| ENABLE REPLICA TRIGGER trigger_name
Determines that the trigger firing mechanism is affected by the configuration variable session_replication_role. When the replication role is origin (default value) or local, a simple trigger is fired.
+
When ENABLE REPLICA is configured for a trigger, it is fired only when the session is in replica mode.
+
| ENABLE ALWAYS TRIGGER trigger_name
Determines that all triggers are fired regardless of the current replication mode.
+
| DISABLE/ENABLE ROW LEVEL SECURITY
Enables or disables row-level access control for a table.
+
If row-level access control is enabled for a data table but no row-level access control policy is defined, the row-level access to the data table is not affected. If row-level access control for a table is disabled, the row-level access to the table is not affected even if a row-level access control policy has been defined. For details, see CREATE ROW LEVEL SECURITY POLICY.
+
| NO FORCE/FORCE ROW LEVEL SECURITY
Forcibly enables or disables row-level access control for a table.
+
By default, the table owner is not affected by the row-level access control feature. However, if row-level access control is forcibly enabled, the table owner (excluding system administrators) wil be affected. System administrators are not affected by any row-level access control policies.
+
+
+
+
There are several clauses of column_clause:
ADD [ COLUMN ] column_name data_type [ compress_mode ] [ COLLATE collation ] [ column_constraint [ ... ] ]
+| MODIFY column_name data_type
+| MODIFY column_name [ CONSTRAINT constraint_name ] NOT NULL [ ENABLE ]
+| MODIFY column_name [ CONSTRAINT constraint_name ] NULL
+| DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ]
+| ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
+| ALTER [ COLUMN ] column_name { SET DEFAULT expression | DROP DEFAULT }
+| ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
+| ALTER [ COLUMN ] column_name SET STATISTICS [PERCENT] integer
+| ADD STATISTICS (( column_1_name, column_2_name [, ...] ))
+| DELETE STATISTICS (( column_1_name, column_2_name [, ...] ))
+| ALTER [ COLUMN ] column_name SET ( {attribute_option = value} [, ... ] )
+| ALTER [ COLUMN ] column_name RESET ( attribute_option [, ... ] )
+| ALTER [ COLUMN ] column_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
Adds a column to a table. If a column is added with ADD COLUMN, all existing rows in the table are initialized with the column's default value (NULL if no DEFAULT clause is specified).
Modifies the data type of an existing column in the table.
+
DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ]
Drops a column from a table. Indexes and constraints related to the column are automatically dropped. If an object not belonging to the table depends on the column, CASCADE must be specified, such as a view.
+
The DROP COLUMN statement does not physically remove the column, but simply makes it invisible to SQL operations. Subsequent INSERT and UPDATE operations in the table will store a NULL value for the column. Therefore, column deletion takes a short period of time but does not immediately release the tablespace on the disks, because the space occupied by the deleted column is not reclaimed. The space will be reclaimed when VACUUM is executed.
+
ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
Modifies the type of a column in a table. Indexes and simple table constraints on the column will automatically use the new data type by reparsing the originally supplied expression.
+
ALTER TYPE requires an entire table be rewritten. This is an advantage sometimes, because it frees up unnecessary space from a table. For example, to reclaim the space occupied by a deleted column, the fastest method is to use the following statement.
+
ALTER TABLE table ALTER COLUMN anycol TYPE anytype;
+
In this statement, anycol indicates any column existing in the table and anytype indicates the type of the prototype of the column. ALTER TYPE does not change the table except that the table is forcibly rewritten. In this way, the data that is no longer used is deleted.
+
ALTER [ COLUMN ] column_name { SET DEFAULT expression | DROP DEFAULT }
Sets or removes the default value for a column. The default values only apply to subsequent INSERT operations; they do not cause rows already in the table to change. Defaults can also be created for views, in which case they are inserted into INSERT statements on the view before the view's ON INSERT rule is applied.
+
ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
Changes whether a column is marked to allow null values or to reject null values. You can only use SET NOT NULL when the column contains no null values.
+
ALTER [ COLUMN ] column_name SET STATISTICS [PERCENT] integer
Specifies the per-column statistics-gathering target for subsequent ANALYZE operations. The target can be set in the range from 0 to 10000. Set it to -1 to revert to using the default system statistics target.
Adds or deletes the declaration of collecting multi-column statistics to collect multi-column statistics as needed when ANALYZE is performed for a table or a database. The statistics about a maximum of 32 columns can be collected at a time. You are not allowed to add or delete such declaration for system catalogs or foreign tables.
+
ALTER [ COLUMN ] column_name SET ( {attribute_option = value} [, ... ] )
Currently, the only defined per-attribute options are n_distinct and n_distinct_inherited. n_distinct affects statistics of a table, while n_distinct_inherited affects the statistics of the table and its subtables. Currently, only SET/RESET n_distinct is supported, and SET/RESET n_distinct_inherited is forbidden.
+
ALTER [ COLUMN ] column_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
Sets the storage mode for a column. This clause specifies whether this column is held inline or in a secondary TOAST table, and whether the data should be compressed. It is set only for row-store tables and is invalid for column-store tables. If it is set for column-store tables, an error will be displayed when the statement is executed. SET STORAGE itself does not change anything in the table. It sets the strategy to be pursued during future table updates.
[ WITH ( {storage_parameter = value} [, ... ] ) ]
+ [ USING INDEX TABLESPACE tablespace_name ]
+
+
+
+
+
Parameter Description
+
+
IF EXISTS
+
Sends a notice instead of an error if no tables have identical names. The notice prompts that the table you are querying does not exist.
+
+
table_name [*] | ONLY table_name | ONLY ( table_name )
+
table_name is the name of the table that you need to modify.
+
If ONLY is specified, only the table is modified. If ONLY is not specified, the table and all subtables will be modified. You can add the asterisk (*) option following the table name to specify that all subtables are scanned, which is the default operation.
+
+
constraint_name
+
Specifies the name of an existing constraint to drop.
+
+
index_name
+
Specifies the name of this index.
+
+
storage_parameter
+
Specifies the name of a storage parameter.
+
+
new_owner
+
Specifies the name of the new table owner.
+
+
new_tablespace
+
Specifies the new name of the tablespace to which the table belongs.
+
+
column_name
+
, column_1_name, column_2_name
Specifies the name of a new or existing column.
+
+
data_type
+
Specifies the type of a new column or a new type of an existing column.
+
+
compress_mode
+
Specifies the compression option of the table, which is only available for row-store tables. The clause specifies the compression algorithm preferentially used by the column.
+
+
collation
+
Specifies the collation rule name of a column. The optional COLLATE clause specifies a collation for the new column; if omitted, the collation is the default for the new column.
+
+
USING expression
+
Specifies how to compute the new column value from the old; if omitted, the default conversion is an assignment cast from old data type to new. A USING clause must be provided if there is no implicit or assignment cast from the old to new type.
+
USING in ALTER TYPE can specify any expression involving the old values of the row; that is, it can refer to any columns other than the one being cast. This allows general casting to be done with the ALTER TYPE syntax. Because of this flexibility, the USING expression is not applied to the column's default value (if any); the result might not be a constant expression as required for a default. This means that when there is no implicit or assignment cast from old to new type, ALTER TYPE might fail to convert the default even though a USING clause is supplied. In such cases, drop the default with DROP DEFAULT, perform the ALTER TYPE, and then use SET DEFAULT to add a suitable new default. Similar considerations apply to indexes and constraints involving the column.
+
+
+
NOT NULL | NULL
+
Sets whether the column allows null values.
+
+
integer
+
Specifies the constant value of a signed integer. When using PERCENT, the range of integer is from 0 to 100.
+
+
attribute_option
+
Specifies an attribute option.
+
+
PLAIN | EXTERNAL | EXTENDED | MAIN
+
Specifies a column storage mode.
+
PLAIN must be used for fixed-length values (such as integers). It must be inline and uncompressed.
MAIN is for inline, compressible data.
EXTERNAL is for external, uncompressed data. Use of EXTERNAL will make substring operations on text and bytea values run faster, at the penalty of increased storage space.
EXTENDED is for external, compressed data. EXTENDED is the default for most data types that support non-PLAIN storage.
+
+
CHECK ( expression )
+
New rows or rows to be updated must satisfy for an expression to be true. If any row produces a false result, an error is raised and the database is not modified.
+
A check constraint specified as a column constraint should reference only the column's values, while an expression appearing in a table constraint can reference multiple columns.
+
Currently, CHECK ( expression ) does not include subqueries and cannot use variables apart from the current column.
+
+
DEFAULT default_expr
+
Assigns a default data value for a column.
+
The data type of the default expression must match the data type of the column.
+
The default expression will be used in any insert operation that does not specify a value for the column. If there is no default value for a column, then the default value is null.
+
+
UNIQUE index_parameters
+
UNIQUE ( column_name [, ... ] ) index_parameters
+
Specifies that a group of one or more columns of a table can contain only unique values.
The primary key constraint specifies that a column or columns of a table can contain only unique (non-duplicate) and non-null values.
+
+
DEFERRABLE | NOT DEFERRABLE | INITIALLY DEFERRED | INITIALLY IMMEDIATE
+
Sets whether the constraint can be deferrable.
+
DEFERRABLE: deferrable to the end of the transaction and checks using SET CONSTRAINTS.
NOT DEFERRABLE: checks immediately after the execution of each command.
INITIALLY IMMEDIATE: checks immediately after the execution of each statement.
INITIALLY DEFERRED: checks when the transaction ends.
+
+
WITH ( {storage_parameter = value} [, ... ] )
+
Specifies an optional storage parameter for a table or an index.
+
+
tablespace_name
+
Specifies the name of the tablespace where the index locates.
+
+
COMPRESS|NOCOMPRESS
+
NOCOMPRESS: If the NOCOMPRESS keyword is specified, the existing compression feature of the table will not be changed.
COMPRESS: If the COMPRESS keyword is specified, the table compression feature will be triggered by batch tuple insertion.
+
+
new_table_name
+
Specifies the new table name.
+
+
new_column_name
+
Specifies the new name of a specific column in a table.
+
+
new_constraint_name
+
Specifies the new name of a table constraint.
+
+
new_schema
+
Specifies the new schema name.
+
+
CASCADE
+
Automatically drops objects that depend on the dropped column or constraint (for example, views referencing the column).
+
+
RESTRICT
+
Refuses to drop the column or constraint if there are any dependent objects. This is the default behavior.
+
+
schema_name
+
Specifies the schema name of a table.
+
]]>
+
+
+
Function
+
ALTER TABLE PARTITION modifies table partition, including adding, deleting, splitting, merging partitions, and modifying partition attributes.
+
+
Precautions
+
The tablespace for the added partition cannot be PG_GLOBAL.
The name of the added partition must be different from names of existing partitions in the partition table.
The partition key of the added partition must be the same type as that of the partition table. The key value of the added partition must exceed the upper limit of the last partition range.
If the number of partitions in the target partition table has reached the maximum (32767), partitions cannot be added.
+
If a partition table has only one partition, the partition cannot be deleted.
Use PARTITION FOR() to choose partitions. The number of specified values in the brackets should be the same as the column number in customized partition, and they must be consistent.
The Value partition table does not support the Alter Partition operation.
Column-store tables and row-store tables cannot be partitioned.
+
+
Syntax
+
Modify the syntax of the table partition.
ALTER TABLE [ IF EXISTS ] { table_name [*] | ONLY table_name | ONLY ( table_name )}
+ action [, ... ];
+
action indicates the following clauses for maintaining partitions. For the partition continuity when multiple clauses are used for partition maintenance, openGauss does DROP PARTITION and then ADD PARTITION, and finally runs the rest clauses in sequence.
The exchange_clause syntax is used to move the data from a general table to a specified partition.
EXCHANGE PARTITION { ( partition_name ) | FOR ( partition_value [, ...] ) }
+ WITH TABLE {[ ONLY ] ordinary_table_name | ordinary_table_name * | ONLY ( ordinary_table_name )}
+ [ { WITH | WITHOUT } VALIDATION ] [ VERBOSE ]
+
The ordinary table and partition whose data is to be exchanged must meet the following requirements:
+
The number of columns of the ordinary table is the same as that of the partition, and their information should be consistent, including: column name, data type, constraint, collation information, storage parameter, and compression information.
The compression information of the ordinary table and partition should be consistent.
The distribution key information of the ordinary table and partition should be consistent.
The number and information of indexes of the ordinary table and partition should be consistent.
The number and information of constraints of the ordinary table and partition should be consistent.
The ordinary table cannot be a temporary table.
+
When the exchange is done, the data and tablespace of the ordinary table and partition are exchanged. The statistics of the ordinary table and partition are no longer inaccurate after the exchange, and they should be analyzed again.
+
The row_clause syntax is used to set row movement of a partitioned table.
{ ENABLE | DISABLE } ROW MOVEMENT
+
+
The merge_clause syntax is used to merge partitions into one.
The split_point_clause syntax is used to specify a split point.
AT ( partition_value ) INTO ( PARTITION partition_name [ TABLESPACE tablespacename ] , PARTITION partition_name [ TABLESPACE tablespacename ] )
+
Column-store tables and row-store tables cannot be partitioned.
The size of the split point should be in the range of partition keys of the partition to be split. The split point can only split one partition into two new partitions.
+
+
The no_split_point_clause syntax does not specify a split point.
The first new partition key specified by partition_less_than_item should be greater than that of the previously split partition (if any), and the last partition key specified by partition_item_clause should equal that of the partition being split.
The first new partition key specified by partition_start_end_item should equal that of the former partition (if any), and the last partition key specified by partition_start_end_item should equal that of the partition being split.
partition_less_than_item supports a maximum of 4 partition keys, while partition_start_end_item supports only one partition key. For details about the supported data types, see PARTITION BY RANGE(parti....
partition_less_than_item and partition_start_end_item cannot be used in the same statement.
+
+
+
The syntax of partition_less_than_item is as follows:
PARTITION partition_name VALUES LESS THAN ( { partition_value | MAXVALUE } [, ...] )
+ [ TABLESPACE tablespacename ]
+
The syntax of partition_start_end_item is as follows. For details about the constraints, see partition_start_end_item syntax.
PARTITION partition_name {
+ {START(partition_value) END (partition_value) EVERY (interval_value)} |
+ {START(partition_value) END ({partition_value | MAXVALUE})} |
+ {START(partition_value)} |
+ {END({partition_value | MAXVALUE})}
+} [TABLESPACE tablespace_name]
+
+
+
+
The add_clause syntax is used to add one or more partitions to a specified partitioned table.
The drop_clause syntax is used to remove a partition from a specified partitioned table.
DROP PARTITION { partition_name | FOR ( partition_value [, ...] ) }
+
+
+
The syntax for modifying the name of a partition is as follows:
ALTER TABLE [ IF EXISTS ] { table_name [*] | ONLY table_name | ONLY ( table_name )}
+ RENAME PARTITION { partion_name | FOR ( partition_value [, ...] ) } TO partition_new_name;
+
+
+
Parameter Description
+
+
table_name
+
Specifies the name of a partitioned table.
+
Value range: an existing table name
+
+
partition_name
+
Specifies the name of a partition.
+
Value range: an existing table name
+
+
tablespacename
+
Specifies which tablespace the partition moves to.
+
Value range: an existing table name
+
+
partition_value
+
Specifies the key value of a partition.
+
The value specified by PARTITION FOR ( partition_value [, ...] ) can uniquely identify a partition.
+
Value range: partition keys for the partition to be renamed
+
+
UNUSABLE LOCAL INDEXES
+
Sets all the indexes unusable in the partition.
+
+
REBUILD UNUSABLE LOCAL INDEXES
+
Rebuilds all the indexes in the partition.
+
+
ENABLE/DISABLE ROW MOVEMET
+
Sets row movement.
+
If the tuple value is updated on the partition key during the UPDATE action, the partition where the tuple is located is altered. Setting this parameter enables error messages to be reported or movement of the tuple between partitions.
+
Value range:
+
ENABLE: Row movement is enabled.
DISABLE: Row movement is disabled.
+
The default value is ENABLE.
+
+
ordinary_table_name
+
Specifies the name of the ordinary table whose data is to be migrated.
+
Value range: an existing table name
+
+
{ WITH | WITHOUT } VALIDATION
+
Checks whether the ordinary table data meets the specified partition key range of the partition to be migrated.
+
Value range:
+
WITH: checks whether the ordinary table data meets the partition key range of the partition to be migrated. If any data does not meet the required range, an error is reported.
WITHOUT: does not check whether the ordinary table data meets the partition key range of the partition to be migrated.
+
The default value is WITH.
+
The check is time consuming, especially when the data volume is large. Therefore, use WITHOUT when you are sure that the current ordinary table data meets the partition key range of the partition to be migrated.
+
+
VERBOSE
+
When VALIDATION is WITH, if the ordinary table contains data that is out of the partition key range, insert the data to the correct partition. If there is no correct partition where the data can be inserted to, an error is reported.
+
Only when VALIDATION is WITH, VERBOSE can be specified.
+
+
+
partition_new_name
+
Specifies the new name of a partition.
+
Value range: a string. It must comply with the naming convention.
+
]]>
+
+
+
Function
+
ALTER TABLESPACE modifies the attributes of a tablespace.
+
+
Precautions
+
Only the owner of a tablespace or a system administrator can execute the ALTER TABLESPACE statement.
To change the owner, you must also be a direct or indirect member of the new owning role.
If new_owner is the same as old_owner, the current user will not be verified. A message indicating successful ALTER execution is displayed.
+
+
+
+
Examples
+
-- Rename the ds_location1 tablespace to ds_location3.
+postgres=# ALTER TABLESPACE ds_location1 RENAME TO ds_location3 ;
+
+-- Change the owner of the ds_location2 tablespace.
+postgres=# ALTER TABLESPACE ds_location2 OWNER TO jay ;
+
+
Syntax
+
The syntax of renaming a tablespace is as follows:
ALTER TABLESPACE tablespace_name
+ RENAME TO new_tablespace_name;
+
The syntax of setting the owner of a tablespace is as follows:
ALTER TABLESPACE tablespace_name
+ OWNER TO new_owner;
+
The syntax of setting the attributes of a tablespace is as follows:
ALTER TABLESPACE tablespace_name
+ SET ( {tablespace_option = value} [, ... ] );
+
The syntax of resetting the attributes of a tablespace is as follows:
The syntax of setting the quota of a tablespace is as follows:
ALTER TABLESPACE tablespace_name
+ RESIZE MAXSIZE { UNLIMITED | 'space_size'};
+
+
+
Parameter Description
+
+
tablespace_name
+
Specifies the tablespace to be modified.
+
Value range: an existing table name
+
+
new_tablespace_name
+
Specifies the new name of a tablespace.
+
The new name cannot start with PG_.
+
Value range: a string. It must comply with the naming convention rule.
+
+
new_owner
+
Specifies the new owner of the tablespace.
+
Value range: an existing username
+
+
tablespace_option
+
Sets or resets the parameters of a tablespace.
+
Value range:
+
seq_page_cost: sets the optimizer to calculate the cost of obtaining disk pages in sequence. The default value is 1.0.
random_page_cost: sets the optimizer to calculate the cost of obtaining disk pages in a non-sequential manner. The default value is 4.0.
The value of random_page_cost is relative to that of seq_page_cost. It is meaningless when the value is equal to or less than the value of seq_page_cost.
The prerequisite for the default value 4.0 is that the optimizer uses indexes to scan table data and the hit ratio of table data in the cache is about 90%.
If the size of the table data space is smaller than that of the physical memory, decrease the value to a proper level. On the contrary, if the hit ratio of table data in the cache is lower than 90%, increase the value.
If random-access memory like SSD is adopted, the value can be decreased to a certain degree to reflect the cost of true random scan.
+
+
+
Value range: a positive floating point number
+
+
RESIZE MAXSIZE
+
Resets the maximum size of tablespace.
+
Value range:
+
UNLIMITED: No limit is set for this tablespace.
Determined by space_size. For details about the format, see CREATE TABLESPACE.
You can also use the following statement to change the value of MAXSIZE:
+
ALTER TABLESPACE tablespace_name RESIZE MAXSIZE
+ { 'UNLIMITED' | 'space_size'};
+
+
+
]]>
+
+
+
Function
+
ALTER TEXT SEARCH CONFIGURATION modifies the definition of a text search configuration. You can modify its mappings from token types to dictionaries, change the configuration's name or owner, or modify the parameters.
+
The ADD MAPPING FOR form installs a list of dictionaries to be consulted for the specified token types; an error will be generated if there is already a mapping for any of the token types.
+
The ALTER MAPPING FOR form removes existing mapping for those token types and then adds specified mappings.
+
ALTER MAPPING REPLACE ... WITH ... and ALTER MAPPING FOR...REPLACE ... WITH ... options replace old_dictionary with new_dictionary. Note that only when pg_ts_config_map has tuples corresponding to maptokentype and old_dictionary, the update will succeed. If the update fails, no messages are returned.
+
The DROP MAPPING FOR form deletes all dictionaries for the specified token types in the text search configuration. If IF EXISTS is not specified and the string type mapping specified by DROP MAPPING FOR does not exist in text search configuration, an error will occur in the database.
+
+
Precautions
+
If a search configuration is referenced (to create indexes), users are not allowed to modify the text search configuration.
To use ALTER TEXT SEARCH CONFIGURATION, you must be the owner of the configuration.
+
+
Examples
+
-- Add text search configuration string mapping.
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ADD MAPPING FOR word WITH simple , english_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+-- Add text search configuration string mapping.
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ADD MAPPING FOR email WITH english_stem , french_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+-- Add text search configuration string mapping.
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ALTER MAPPING REPLACE french_stem with german_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+
Syntax
+
Add text search configuration string mapping.
+
ALTER TEXT SEARCH CONFIGURATION name
+ ADD MAPPING FOR token_type [, ... ] WITH dictionary_name [, ... ];
+
Modify the text search configuration dictionary syntax.
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING FOR token_type [, ... ] REPLACE old_dictionary WITH new_dictionary;
+
Modify the text search configuration string.
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING FOR token_type [, ... ] WITH dictionary_name [, ... ];
+
Change the text search configuration dictionary.
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING REPLACE old_dictionary WITH new_dictionary;
+
Remove text search configuration string mapping.
+
ALTER TEXT SEARCH CONFIGURATION name
+ DROP MAPPING [ IF EXISTS ] FOR token_type [, ... ];
+
Rename the owner of text search configuration.
+
ALTER TEXT SEARCH CONFIGURATION name OWNER TO new_owner;
+
Rename the text search configuration.
+
ALTER TEXT SEARCH CONFIGURATION name RENAME TO new_name;
+
Rename the namespace of text search configuration.
+
ALTER TEXT SEARCH CONFIGURATION name SET SCHEMA new_schema;
+
Modify the attributes of the text search configuration.
+
ALTER TEXT SEARCH CONFIGURATION name SET ( { configuration_option = value } [, ...] );
+
Reset the attributes of text search configuration.
+
ALTER TEXT SEARCH CONFIGURATION name RESET ( {configuration_option} [, ...] );
+
+
Parameter Description
+
+
name
+
Specifies the name (optionally schema-qualified) of an existing text search configuration.
+
+
token_type
+
Specifies the name of a token type that is emitted by the configuration's parser. For details, see Parser.
+
+
dictionary_name
+
Specifies the name of a text search dictionary. If multiple dictionaries are listed, they are searched in the specified order.
+
+
old_dictionary
+
Specifies the name of a text search dictionary to be replaced in the mapping.
+
+
new_dictionary
+
Specifies the name of a text search dictionary to be substituted for old_dictionary.
+
+
new_owner
+
Specifies the new owner of the text search configuration.
+
+
new_name
+
Specifies the new name of the text search configuration.
+
+
new_schema
+
Specifies the new schema for the text search configuration.
Specifies the value of text search configuration option.
+
]]>
+
+
+
Function
+
ALTER TEXT SEARCH DICTIONARY modifies the definition of a full-text search dictionary, including its parameters, name, owner, and schema.
+
+
Precautions
+
Predefined dictionaries do not support the ALTER operations.
Only the owner of a dictionary or a system administrator can perform the ALTER operations.
After a dictionary is created or modified, any modification to the customized dictionary definition file in the filepath directory does not affect the dictionary in the database. To use these modifications in the database, run the ALTER TEXT SEARCH DICTIONARY statement to update the definition file of the corresponding dictionary.
+
+
Examples
+
-- Modify the definition of stop words in Snowball dictionaries. Retain the values of other parameters.
+postgres=# ALTER TEXT SEARCH DICTIONARY my_dict ( StopWords = newrussian , FilePath = ' file:///home/dicts ' ) ;
+
+-- Modify the Language parameter in Snowball dictionaries and delete the definition of stop words.
+postgres=# ALTER TEXT SEARCH DICTIONARY my_dict ( Language = dutch , StopWords ) ;
+
+-- Update the dictionary definition and do not change any other content.
+postgres=# ALTER TEXT SEARCH DICTIONARY my_dict ( dummy ) ;
+
+
Syntax
+
Modify the dictionary definition.
ALTER TEXT SEARCH DICTIONARY name (
+ option [ = value ] [, ... ]
+);
+
+
Rename a dictionary.
ALTER TEXT SEARCH DICTIONARY name RENAME TO new_name;
+
Set the schema of the dictionary.
ALTER TEXT SEARCH DICTIONARY name SET SCHEMA new_schema;
+
Change the owner of the dictionary.
ALTER TEXT SEARCH DICTIONARY name OWNER TO new_owner;
+
+
+
Parameter Description
+
+
name
+
Specifies the name of an existing dictionary. (If you do not specify a schema name, the dictionary in the current schema will be used.)
+
Value range: an existing dictionary name
+
+
option
+
Specifies the parameter name to be modified. Each type of dictionaries has a template containing their custom parameters. Parameters function in a way irrelevant to their setting sequence. For details about the parameters, see option.
+
The value of TEMPLATE in the dictionary cannot be changed.
To specify a dictionary, specify both the dictionary definition file path (FILEPATH) and the file name.
The name of a dictionary definition file can contain only lowercase letters, digits, and underscores (_).
+
+
+
value
+
Specifies the new value of a parameter. If the equal sign (=) and value are omitted, the previous settings of the option are deleted and the default value is used.
+
Value range: valid values defined by option.
+
+
new_name
+
Specifies the new name of a dictionary.
+
Value range: a string, which complies with the identifier naming convention. A value can contain a maximum of 63 characters.
+
+
new_owner
+
Specifies the new owner of a dictionary.
+
Value range: an existing username
+
+
new_schema
+
Specifies the new schema of a dictionary.
+
Value range: an existing schema
+
]]>
+
+
+
Function
+
ALTER TRIGGER modifies the definition of a trigger.
+
+
Precautions
+
Only the owner of a table where the trigger is created and a system administrator can run the ALTER TRIGGER statement.
+
+
Examples
+
-- Modify a trigger.
+postgres=# ALTER TRIGGER delete_trigger ON test_trigger_src_tbl RENAME TO delete_trigger_renamed ;
+
+-- Disable insert_trigger.
+postgres=# ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER insert_trigger ;
+
+-- Disable all triggers on the current table.
+postgres=# ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER ALL ;
+
+
Syntax
+
ALTER TRIGGER trigger_name ON table_name RENAME TO new_name;
+
+
Parameter Description
+
+
trigger_name
+
Specifies the name of the trigger to be modified.
+
Value range: an existing trigger
+
+
table_name
+
Specifies the name of the table where the trigger to be modified is located.
+
Value range: an existing table having a trigger
+
+
new_name
+
Specifies the new name after modification.
+
Value range: a string, which complies with the identifier naming convention. A value contains a maximum of 63 characters and cannot be the same as other triggers on the same table.
+
]]>
+
+
+
Function
+
ALTER TYPE modifies the definition of a type.
+
+
Syntax
+
Modify a type.
ALTER TYPE name action [, ... ]
+ALTER TYPE name OWNER TO { new_owner | CURRENT_USER | SESSION_USER }
+ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ]
+ALTER TYPE name RENAME TO new_name
+ALTER TYPE name SET SCHEMA new_schema
+ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ]
+ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value
+
+where action is one of:
+ ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
+ DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ]
+ ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
+
Add a new attribute to a composite type.
ALTER TYPE name ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
+
+
+
Parameter Description
+
+
name
+
Specifies the name of an existing type that needs to be modified (optionally schema-qualified).
+
]]>
+
+
+
Function
+
ALTER USER modifies the attributes of a database user.
+
+
Precautions
+
Session parameters modified by ALTER USER apply to a specified user and take effect in the next session.
Change the value of a specified parameter associated with the user.
ALTER USER user_name
+ SET configuration_parameter { { TO | = } { value | DEFAULT } | FROM CURRENT };
+
Reset the value of a specified parameter associated with the user.
ALTER USER user_name
+ RESET { configuration_parameter | ALL };
+
+
+
Parameter Description
+
+
user_name
+
Specifies the current username.
+
Value range: an existing username
+
+
new_password
+
Specifies a new password.
+
The new password must:
+
Differ from the old password.
Contain at least eight characters. This is the default length.
Differ from the username or the username spelled backward.
Contain at least three types of the following four types of characters: uppercase characters (A to Z), lowercase characters (a to z), digits (0 to 9), and special characters, including: ~!@#$%^&*()-_=+\|[{}];:,<.>/?
+
Value range: a string
+
+
old_password
+
Specifies the old password.
+
+
ACCOUNT LOCK | ACCOUNT UNLOCK
+
ACCOUNT LOCK: locks an account to forbid login to databases.
ACCOUNT UNLOCK: unlocks an account to allow login to databases.
+
+
PGUSER
+
In the current version, the PGUSER attribute of a user cannot be modified.
+
]]>
+
+
+
Function
+
ALTER VIEW modifies all auxiliary attributes of a view. (To modify the query definition of a view, use CREATE OR REPLACE VIEW.)
+
+
Precautions
+
Only the owner of a view can use ALTER VIEW.
To change the schema of a view, you must have the CREATE permission on the new schema.
To change the owner of a view, you must be a direct or indirect member of the new owning role, and the member must have the CREATE permission on the view's schema.
An administrator can change the owner relationship of any view.
+
+
Examples
+
-- Rename a view.
+postgres=# ALTER VIEW tpcds.customer_details_view_v1 RENAME TO customer_details_view_v2 ;
+
+-- Change the schema of a view.
+postgres=# ALTER VIEW tpcds.customer_details_view_v2 SET schema public ;
+
+
Syntax
+
Set the default value of a view column.
ALTER VIEW [ IF EXISTS ] view_name
+ ALTER [ COLUMN ] column_name SET DEFAULT expression;
+
Remove the default value of a view column.
ALTER VIEW [ IF EXISTS ] view_name
+ ALTER [ COLUMN ] column_name DROP DEFAULT;
+
Change the owner of a view.
ALTER VIEW [ IF EXISTS ] view_name
+ OWNER TO new_owner;
+
Rename a view.
ALTER VIEW [ IF EXISTS ] view_name
+ RENAME TO new_name;
+
Set the schema of a view.
ALTER VIEW [ IF EXISTS ] view_name
+ SET SCHEMA new_schema;
+
Set the options of a view.
ALTER VIEW [ IF EXISTS ] view_name
+ SET ( { view_option_name [ = view_option_value ] } [, ... ] );
+
Reset the options of a view.
ALTER VIEW [ IF EXISTS ] view_name
+ RESET ( view_option_name [, ... ] );
+
+
+
Parameter Description
+
+
IF EXISTS
+
If this option is used, no error is generated when the view does not exist, and only a message is displayed.
+
+
view_name
+
Specifies the view name, which can be schema-qualified.
+
Value range: a string. It must comply with the naming convention rule.
+
+
column_name
+
Specifies an optional list of names to be used for columns of the view. If not given, the column names are deduced from the query.
+
Value range: a string. It must comply with the naming convention rule.
+
+
SET/DROP DEFAULT
+
Sets or deletes the default value of a column. this parameter does not take effect.
+
+
new_owner
+
Specifies the new owner of a view.
+
+
new_name
+
Specifies the new view name.
+
+
new_schema
+
Specifies the new schema of the view.
+
+
view_option_name [ = view_option_value ]
+
Specifies an optional parameter for a view.
+
Currently, view_option_name supports only the security_barrier parameter. This parameter is used when the view attempts to provide row-level security.
+
Value range: Boolean type, TRUE, and FALSE.
+
]]>
+
+
+
Function
+
ANALYZE collects statistics about ordinary tables in a database, and stores the results in the PG_STATISTIC system catalog. The execution plan generator uses these statistics to determine which one is the most effective execution plan.
+
If no parameter is specified, ANALYZE analyzes each table and partitioned table in the current database. You can also specify the table_name, column, and partition_name parameters to restrict the analysis to a specific table, column, or partitioned table.
+
ANALYZE | ANALYSE VERIFY is used to check whether data files of common tables (row-store and column-store tables) in a database are damaged.
+
+
Precautions
+
Non-temporary tables cannot be analyzed in an anonymous block, transaction block, function, or stored procedure. Temporary tables in a stored procedure can be analyzed but their statistics updates cannot be rolled back.
+
The ANALYZE VERIFY operation is used to detect abnormal scenarios. The RELEASE version is required. In the ANALYZE VERIFY scenario, remote read is not triggered. Therefore, the remote read parameter does not take effect. If the system detects that a page is damaged due to an error in a key system table, the system directly reports an error and does not continue the detection.
+
+
Examples
+
postgres=# CREATE TABLE customer_info
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER
+ )
+ ;
+
+-- Create a partitioned table.
+postgres=# CREATE TABLE customer_par
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER
+ )
+PARTITION BY RANGE ( WR_RETURNED_DATE_SK )
+ (
+PARTITION P1 VALUES LESS THAN ( 2452275 ) ,
+PARTITION P2 VALUES LESS THAN ( 2452640 ) ,
+PARTITION P3 VALUES LESS THAN ( 2453000 ) ,
+PARTITION P4 VALUES LESS THAN ( MAXVALUE )
+ )
+ENABLE ROW MOVEMENT ;
+
+-- Run ANALYZE to update statistics.
+postgres=# ANALYZE customer ;
+
+-- Run ANALYZE VERBOSE statement to update statistics and display table information.
+postgres=# ANALYZE VERBOSE customer_info ;
+INFO: analyzing "cstore.pg_delta_3394584009" ( cn_5002 pid=53078 )
+INFO: analyzing "public.customer_info" ( cn_5002 pid=53078 )
+INFO: analyzing "public.customer_info" inheritance tree ( cn_5002 pid=53078 )
+ANALYZE
+If any environment-related fault occurs , check the logs of the primary node of the database.
+
+-- Delete the table.
+postgres=# DROP TABLE customer ;
+postgres=# DROP TABLE customer_par ;
+
An ordinary partitioned table supports the syntax but not the function of collecting statistics about specified partitions.
+
+
+
+
Parameter Description
+
+
VERBOSE
+
Enables the display of progress messages.
+
If VERBOSE is specified, ANALYZE displays the progress information, indicating the table that is being processed. Statistics about tables are also displayed.
+
+
+
table_name
+
Specifies the name (possibly schema-qualified) of a specific table to analyze. If omitted, all regular tables (but not foreign tables) in the current database are analyzed.
+
Currently, you can use ANALYZE to collect statistics only from row-store tables and column-store tables.
+
Value range: an existing table name
+
+
column_name
+
, column_1_name, column_2_name
Specifies the name of a specific column to analyze. All columns are analyzed by default.
+
Value range: an existing column name
+
+
partition_name
+
Assumes the table is a partitioned table. You can specify partition_name following the keyword PARTITION to analyze the statistics of this table. Currently, ANALYZE can be performed on partitioned tables, but statistics of specified partitions cannot be analyzed.
+
Value range: a partition name of a table
+
+
index_name
+
Specifies the name of the specific index table to be analyzed (possibly schema-qualified).
+
Value range: an existing table name
+
+
FAST|COMPLETE
+
For a row-store table, the FAST mode verifies the CRC and page header of the row-store table. If the verification fails, an alarm is generated. In COMPLETE mode, the pointer and tuple of the row-store table are parsed and verified. For a column-store table, the FAST mode verifies the CRC and magic of the column-store table. If the verification fails, an alarm is generated. In COMPLETE mode, the CU of the column-store table is parsed and verified.
+
+
CASCADE
+
In CASCADE mode, all indexes of the current table are verified.
+
]]>
+
+
+
Function
+
ANALYZE collects statistics about ordinary tables in a database, and stores the results in the PG_STATISTIC system catalog. The execution plan generator uses these statistics to determine which one is the most effective execution plan.
+
If no parameter is specified, ANALYZE analyzes each table and partitioned table in the current database. You can also specify the table_name, column, and partition_name parameters to restrict the analysis to a specific table, column, or partitioned table.
+
ANALYZE | ANALYSE VERIFY is used to check whether data files of common tables (row-store and column-store tables) in a database are damaged.
+
+
Precautions
+
Non-temporary tables cannot be analyzed in an anonymous block, transaction block, function, or stored procedure. Temporary tables in a stored procedure can be analyzed but their statistics updates cannot be rolled back.
+
The ANALYZE VERIFY operation is used to detect abnormal scenarios. The RELEASE version is required. In the ANALYZE VERIFY scenario, remote read is not triggered. Therefore, the remote read parameter does not take effect. If the system detects that a page is damaged due to an error in a key system table, the system directly reports an error and does not continue the detection.
+
+
Examples
+
postgres=# CREATE TABLE customer_info
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER
+ )
+ ;
+
+-- Create a partitioned table.
+postgres=# CREATE TABLE customer_par
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER
+ )
+PARTITION BY RANGE ( WR_RETURNED_DATE_SK )
+ (
+PARTITION P1 VALUES LESS THAN ( 2452275 ) ,
+PARTITION P2 VALUES LESS THAN ( 2452640 ) ,
+PARTITION P3 VALUES LESS THAN ( 2453000 ) ,
+PARTITION P4 VALUES LESS THAN ( MAXVALUE )
+ )
+ENABLE ROW MOVEMENT ;
+
+-- Run ANALYZE to update statistics.
+postgres=# ANALYZE customer ;
+
+-- Run ANALYZE VERBOSE statement to update statistics and display table information.
+postgres=# ANALYZE VERBOSE customer_info ;
+INFO: analyzing "cstore.pg_delta_3394584009" ( cn_5002 pid=53078 )
+INFO: analyzing "public.customer_info" ( cn_5002 pid=53078 )
+INFO: analyzing "public.customer_info" inheritance tree ( cn_5002 pid=53078 )
+ANALYZE
+If any environment-related fault occurs , check the logs of the primary node of the database.
+
+-- Delete the table.
+postgres=# DROP TABLE customer ;
+postgres=# DROP TABLE customer_par ;
+
An ordinary partitioned table supports the syntax but not the function of collecting statistics about specified partitions.
+
+
+
+
Parameter Description
+
+
VERBOSE
+
Enables the display of progress messages.
+
If VERBOSE is specified, ANALYZE displays the progress information, indicating the table that is being processed. Statistics about tables are also displayed.
+
+
+
table_name
+
Specifies the name (possibly schema-qualified) of a specific table to analyze. If omitted, all regular tables (but not foreign tables) in the current database are analyzed.
+
Currently, you can use ANALYZE to collect statistics only from row-store tables and column-store tables.
+
Value range: an existing table name
+
+
column_name
+
, column_1_name, column_2_name
Specifies the name of a specific column to analyze. All columns are analyzed by default.
+
Value range: an existing column name
+
+
partition_name
+
Assumes the table is a partitioned table. You can specify partition_name following the keyword PARTITION to analyze the statistics of this table. Currently, ANALYZE can be performed on partitioned tables, but statistics of specified partitions cannot be analyzed.
+
Value range: a partition name of a table
+
+
index_name
+
Specifies the name of the specific index table to be analyzed (possibly schema-qualified).
+
Value range: an existing table name
+
+
FAST|COMPLETE
+
For a row-store table, the FAST mode verifies the CRC and page header of the row-store table. If the verification fails, an alarm is generated. In COMPLETE mode, the pointer and tuple of the row-store table are parsed and verified. For a column-store table, the FAST mode verifies the CRC and magic of the column-store table. If the verification fails, an alarm is generated. In COMPLETE mode, the CU of the column-store table is parsed and verified.
+
+
CASCADE
+
In CASCADE mode, all indexes of the current table are verified.
+
]]>
+
+
+
Function
+
BEGIN may be used to initiate an anonymous block or a single transaction. This section describes the syntax of BEGIN used to initiate an anonymous block. For details about the BEGIN syntax that initiates transactions, see START TRANSACTION.
+
An anonymous block is a structure that can dynamically create and execute stored procedure code instead of permanently storing code as a database object in the database.
Specifies the name of the schema where a function or stored procedure is located.
+
+
func_name
+
Specifies the name of the function or stored procedure to be called.
+
Value range: an existing function name
+
+
param_expr
+
Specifies a list of parameters in the function. Use := or => to separate a parameter name and its value. This method allows parameters to be placed in any order. If only parameter values are in the list, the value order must be the same as that defined in the function or stored procedure.
+
Value range: an existing function parameter name or stored procedure parameter name
+
The parameters include input parameters (whose name and type are separated by IN) and output parameters (whose name and type are separated by OUT). When you run the CALL statement to call a function or stored procedure, the parameter list must contain an output parameter for non-overloaded functions. You can set the output parameter to a variable or any constant. For details, see Examples. For an overloaded package function, the parameter list can have no output parameter, but the function may not be found. If an output parameter is contained, it must be a constant.
+
+
]]>
+
+
+
Function
+
A checkpoint is a point in the transaction log sequence at which all data files have been updated to reflect the information in the log. All data files will be flushed to a disk.
+
CHECKPOINT forces a transaction log checkpoint. By default, WALs periodically specify checkpoints in a transaction log. You may use gs_guc to specify run-time parameters checkpoint_segments and checkpoint_timeout to adjust the atomized checkpoint intervals.
+
+
Examples
+
-- Set a checkpoint.
+postgres=# CHECKPOINT ;
+
+
Syntax
+
CHECKPOINT;
+
]]>
+
+
+
Function
+
CLOSE frees the resources associated with an open cursor.
+
+
Precautions
+
After a cursor is closed, no subsequent operations are allowed on it.
A cursor should be closed when it is no longer needed.
Every non-holdable open cursor is implicitly closed when a transaction is terminated by COMMIT or ROLLBACK.
A holdable cursor is implicitly closed if the transaction that created it aborts by ROLLBACK.
If the cursor creation transaction is successfully committed, the holdable cursor remains open until an explicit CLOSE operation is executed, or the client disconnects.
openGauss does not have an explicit OPEN cursor statement. A cursor is considered open when it is declared. You can view all available cursors by querying the pg_cursors system view.
+
+
Examples
+
-- Close the cursor and commit the transaction.
+postgres=# CLOSE cursor1 ;
+
+-- Close the cursor and commit the transaction.
+postgres=# CLOSE cursor2 ;
+
+-- Close the cursor.
+postgres=# CLOSE cursor1 ;
+
+
Syntax
+
CLOSE { cursor_name | ALL } ;
+
+
Parameter Description
+
+
cursor_name
+
Specifies the name of a cursor to be closed.
+
+
ALL
+
Closes all open cursors.
+
]]>
+
+
+
Function
+
CLUSTER is used to cluster a table based on an index.
+
CLUSTER instructs openGauss to cluster the table specified by table_name based on the index specified by index_name. The index must have been defined by table_name.
+
When a table is clustered, it is physically reordered based on the index information. Clustering is a one-time operation. When the table is subsequently updated, the changes are not clustered. That is, no attempt is made to store new or updated rows according to their index order.
+
When a table is clustered, openGauss records which index the table was clustered by. The form CLUSTER table_name reclusters the table using the same index as before. You can also use the CLUSTER or SET WITHOUT CLUSTER form of ALTER TABLE to set the index to be used for future cluster operations, or to clear any previous settings.
+
CLUSTER without any parameter reclusters all the previously-clustered tables in the current database that the calling user owns, or all such tables if called by an administrator.
+
When a table is being clustered, an ACCESS EXCLUSIVE lock is acquired on it. This prevents any other database operations (both read and write) from being performed on the table until the CLUSTER is finished.
+
+
Precautions
+
Only row-store B-tree indexes support CLUSTER.
+
In the case where you are accessing single rows randomly within a table, the actual order of the data in the table is unimportant. However, if you tend to access some data more than others, and there is an index that groups them together, it is helpful by using CLUSTER. If you are requesting a range of indexed values from a table, or a single indexed value that has multiple rows that match, CLUSTER will help because once the index identifies the table page for the first row that matches, all other rows that match are probably already on the same table page, and so you save disk accesses and speed up the query.
+
When an index scan is used, a temporary copy of the table is created that contains the table data in the index order. Temporary copies of each index on the table are created as well. Therefore, you need free space on disk at least equal to the sum of the table size and the total index size.
+
Because CLUSTER remembers which indexes are clustered, one can cluster the tables manually the first time, then set up a time like VACUUM without any parameters, so that the desired tables are periodically reclustered.
+
Because the optimizer records statistics about the ordering of tables, it is advisable to run ANALYZE on the newly clustered table. Otherwise, the optimizer might make poor choices of query plans.
+
CLUSTER cannot be executed in transactions.
+
+
Examples
+
-- Cluster the tpcds.inventory_p1 table.
+postgres=# CLUSTER tpcds.inventory_p1 USING ds_inventory_p1_index1 ;
+
+-- Cluster the p3 partition.
+postgres=# CLUSTER tpcds.inventory_p1 PARTITION ( p3 ) USING ds_inventory_p1_index1 ;
+
+-- Cluster the tables that can be clustered in the database.
+postgres=# CLUSTER ;
+
+
Syntax
+
Cluster a table.
CLUSTER [ VERBOSE ] table_name [ USING index_name ];
COMMENT defines or changes the comment of an object.
+
+
Precautions
+
Each object stores only one comment. Therefore, you need to modify a comment and issue a new COMMENT command to the same object. To delete the comment, write NULL at the position of the text string. When an object is deleted, the comment is automatically deleted.
Currently, there is no security protection for viewing comments. Any user connected to a database can view all the comments for objects in the database. For shared objects such as databases, roles, and tablespaces, comments are stored globally so any user connected to any database in the cluster can see all the comments for shared objects. Therefore, do not put security-critical information in comments.
For most objects, only the owner of the object can set comments. Roles do not have owners, so the rule for COMMENT ON ROLE is that you must be an administrator to comment on an administrator role, or have the CREATEROLE permission to comment on non-administrator roles. A system administrator can comment on all objects.
+
+
Examples
+
-- Comment out the tpcds.customer_demographics_t2.cd_demo_sk column.
+postgres=# COMMENT ON COLUMN tpcds.customer_demographics_t2.cd_demo_sk IS ' Primary key of customer demographics table. ' ;
+
+-- Comment out the tpcds.customer_details_view_v2 view.
+postgres=# COMMENT ON VIEW tpcds.customer_details_view_v2 IS ' View of customer detail ' ;
+
+
Syntax
+
COMMENT ON
+{
+ AGGREGATE agg_name (agg_type [, ...] ) |
+ CAST (source_type AS target_type) |
+ COLLATION object_name |
+ COLUMN { table_name.column_name | view_name.column_name } |
+ CONSTRAINT constraint_name ON table_name |
+ CONVERSION object_name |
+ DATABASE object_name |
+ DOMAIN object_name |
+ EXTENSION object_name |
+ FOREIGN DATA WRAPPER object_name |
+ FOREIGN TABLE object_name |
+ FUNCTION function_name ( [ {[ argmode ] [ argname ] argtype} [, ...] ] ) |
+ INDEX object_name |
+ LARGE OBJECT large_object_oid |
+ OPERATOR operator_name (left_type, right_type) |
+ OPERATOR CLASS object_name USING index_method |
+ OPERATOR FAMILY object_name USING index_method |
+ [ PROCEDURAL ] LANGUAGE object_name |
+ ROLE object_name |
+ SCHEMA object_name |
+ SERVER object_name |
+ TABLE object_name |
+ TABLESPACE object_name |
+ TEXT SEARCH CONFIGURATION object_name |
+ TEXT SEARCH DICTIONARY object_name |
+ TEXT SEARCH PARSER object_name |
+ TEXT SEARCH TEMPLATE object_name |
+ TYPE object_name |
+ VIEW object_name
+}
+ IS 'text';
+
+
Parameter Description
+
+
agg_name
+
Specifies the new name of an aggregation function.
+
+
agg_type
+
Specifies the data type of the aggregation function parameters.
+
+
source_type
+
Specifies the source data type of the cast.
+
+
target_type
+
Specifies the target data type of the cast.
+
+
object_name
+
Specifies the name of an object.
+
+
table_name.column_name
+
view_name.column_name
+
Specifies the column whose comment is defined or modified. You can add the table name or view name as the prefix.
+
+
constraint_name
+
Specifies the table constraint whose comment is defined or modified.
+
+
table_name
+
Specifies the name of a table.
+
+
function_name
+
Specifies the function whose comment is defined or modified.
+
+
argmode,argname,argtype
+
Specifies the schema, name, and type of the function parameters.
+
+
large_object_oid
+
Specifies the OID of the large object whose comment is defined or modified.
+
+
operator_name
+
Specifies the name of the operator.
+
+
left_type,right_type
+
Specifies the data type of the operator parameters (optionally schema-qualified). If the prefix or suffix operator does not exist, the NONE option can be added.
+
+
text
+
Specifies the comment content.
+
]]>
+
+
+
Function
+
COMMIT or END commits all operations of a transaction.
+
+
Precautions
+
Only the creator of a transaction or a system administrator can run the COMMIT command. The creation and commit operations must be in different sessions.
+
+
Examples
+
-- Create a table.
+postgres=# CREATE TABLE tpcds.customer_demographics_t2
+ (
+CD_DEMO_SK INTEGER NOT NULL ,
+CD_GENDER CHAR ( 1 ) ,
+CD_MARITAL_STATUS CHAR ( 1 ) ,
+CD_EDUCATION_STATUS CHAR ( 20 ) ,
+CD_PURCHASE_ESTIMATE INTEGER ,
+CD_CREDIT_RATING CHAR ( 10 ) ,
+CD_DEP_COUNT INTEGER ,
+CD_DEP_EMPLOYED_COUNT INTEGER ,
+CD_DEP_COLLEGE_COUNT INTEGER
+ )
+WITH ( ORIENTATION = COLUMN , COMPRESSION=MIDDLE )
+ ;
+
+-- Start a transaction.
+postgres=# START TRANSACTION ;
+
+-- Insert data.
+postgres=# INSERT INTO tpcds.customer_demographics_t2 VALUES ( 1 , ' M ' , ' U ' , ' DOCTOR DEGREE ' , 1200 , ' GOOD ' , 1 , 0 , 0 ) ;
+postgres=# INSERT INTO tpcds.customer_demographics_t2 VALUES ( 2 , ' F ' , ' U ' , ' MASTER DEGREE ' , 300 , ' BAD ' , 1 , 0 , 0 ) ;
+
+-- Commit the transaction to make all changes permanent.
+postgres=# COMMIT ;
+
+-- Query data.
+postgres=# SELECT * FROM tpcds.customer_demographics_t2 ;
+
+-- Delete the tpcds.customer_demographics_t2 table.
+postgres=# DROP TABLE tpcds.customer_demographics_t2 ;
+
+
Syntax
+
{ COMMIT | END } [ WORK | TRANSACTION ] ;
+
+
Parameter Description
+
+
COMMIT | END
+
Commits the current transaction and makes all changes made by the transaction become visible to others.
+
+
WORK | TRANSACTION
+
Specifies an optional keyword, which has no effect except increasing readability.
+
]]>
+
+
+
Function
+
COMMIT or END commits all operations of a transaction.
+
+
Precautions
+
Only the creator of a transaction or a system administrator can run the COMMIT command. The creation and commit operations must be in different sessions.
+
+
Examples
+
-- Create a table.
+postgres=# CREATE TABLE tpcds.customer_demographics_t2
+ (
+CD_DEMO_SK INTEGER NOT NULL ,
+CD_GENDER CHAR ( 1 ) ,
+CD_MARITAL_STATUS CHAR ( 1 ) ,
+CD_EDUCATION_STATUS CHAR ( 20 ) ,
+CD_PURCHASE_ESTIMATE INTEGER ,
+CD_CREDIT_RATING CHAR ( 10 ) ,
+CD_DEP_COUNT INTEGER ,
+CD_DEP_EMPLOYED_COUNT INTEGER ,
+CD_DEP_COLLEGE_COUNT INTEGER
+ )
+WITH ( ORIENTATION = COLUMN , COMPRESSION=MIDDLE )
+ ;
+
+-- Start a transaction.
+postgres=# START TRANSACTION ;
+
+-- Insert data.
+postgres=# INSERT INTO tpcds.customer_demographics_t2 VALUES ( 1 , ' M ' , ' U ' , ' DOCTOR DEGREE ' , 1200 , ' GOOD ' , 1 , 0 , 0 ) ;
+postgres=# INSERT INTO tpcds.customer_demographics_t2 VALUES ( 2 , ' F ' , ' U ' , ' MASTER DEGREE ' , 300 , ' BAD ' , 1 , 0 , 0 ) ;
+
+-- Commit the transaction to make all changes permanent.
+postgres=# COMMIT ;
+
+-- Query data.
+postgres=# SELECT * FROM tpcds.customer_demographics_t2 ;
+
+-- Delete the tpcds.customer_demographics_t2 table.
+postgres=# DROP TABLE tpcds.customer_demographics_t2 ;
+
+
Syntax
+
{ COMMIT | END } [ WORK | TRANSACTION ] ;
+
+
Parameter Description
+
+
COMMIT | END
+
Commits the current transaction and makes all changes made by the transaction become visible to others.
+
+
WORK | TRANSACTION
+
Specifies an optional keyword, which has no effect except increasing readability.
+
]]>
+
+
+
Function
+
COMMIT PREPARED commits a prepared two-phase transaction.
+
+
Precautions
+
The function is only available in maintenance mode (when GUC parameter xc_maintenance_mode is on). Exercise caution when enabling the mode. It is used by maintenance engineers for troubleshooting. Common users should not use the mode.
Only the transaction creators or system administrators can run the COMMIT PREPARED command. The creation and commit operations must be in different sessions.
The transaction function is maintained automatically by the database, and should be not visible to users.
+
+
Syntax
+
COMMIT PREPARED transaction_id ;
+COMMIT PREPARED transaction_id WITH CSN;
+
+
Parameter Description
+
+
transaction_id
+
Specifies the identifier of the transaction to be committed. The identifier must be different from those for current prepared transactions.
+
]]>
+
+
+
Function
+
COPY copies data between tables and files.
+
COPY FROM copies data from a file to a table, and COPY TO copies data from a table to a file.
+
+
Precautions
+
To run the COPY FROM FILENAME or COPY TO FILENAME statement, you must have the SYSADMIN permission. By default, user SYSADMIN is not allowed to run the COPY FROM FILENAME or COPY TO FILENAME statement on database configuration files, key files, certificate files, and audit logs, preventing user SYSADMIN from viewing or modifying sensitive files without authorization. To grant the permission, you need to change the setting of enable_copy_server_files.
COPY applies only to tables but not views.
To insert data to a table, you must have the permission to insert data.
If a list of columns is specified, COPY copies only the data of the specified columns between the file and the table. If a table has any columns that are not in the column list, COPY FROM inserts default values for those columns.
If a data source file is specified, the server must be able to access the file. If STDIN is specified, data flows between the client and the server. When entering data, use the TAB key to separate the columns of the table and use a backslash and a period (\.) in a new row to indicate the end of the input.
COPY FROM throws an error if any row in the data file contains more or fewer columns than expected.
The end of the data can be represented by a line that contains only a backslash and a period (\.). If data is read from a file, the end flag is unnecessary. If data is copied between client applications, an end tag must be provided.
In COPY FROM, \N is an empty string. To enter the actual value \N, use \\N.
+
+
Examples
+
-- Copy data from the tpcds.ship_mode file to the /home/omm/ds_ship_mode.dat file:
+postgres=# COPY tpcds.ship_mode TO ' /home/omm/ds_ship_mode.dat ' ;
+
+-- Output tpcds.ship_mode to stdout.
+postgres=# COPY tpcds.ship_mode TO stdout;
+
+-- Copy data from stdin to the tpcds.ship_mode_t1 table.
+postgres=# COPY tpcds.ship_mode_t1 FROM stdin ;
+
+-- Copy data from the /home/omm/ds_ship_mode.dat file to the tpcds.ship_mode_t1 table.
+postgres=# COPY tpcds.ship_mode_t1 FROM ' /home/omm/ds_ship_mode.dat ' ;
+
+-- Copy data from the /home/omm/ds_ship_mode.dat file to the tpcds.ship_mode_t1 table, with the import format set to TEXT ( format 'text' ) , the delimiter set to \t' ( delimiter E'\t' ) , excessive columns ignored ( ignore_extra_data 'true' ) , and characters not escaped ( noescaping 'true' ) .
+postgres=# COPY tpcds.ship_mode_t1 FROM ' /home/omm/ds_ship_mode.dat ' WITH ( format ' text ' , delimiter E ' \t ' , ignore_extra_data ' true ' , noescaping ' true ' ) ;
+
+-- Copy data from the /home/omm/ds_ship_mode.dat file to the tpcds.ship_mode_t1 table, with the import format set to FIXED, fixed-length format specified ( FORMATTER ( SM_SHIP_MODE_SK ( 0, 2 ) , SM_SHIP_MODE_ID ( 2,16 ) , SM_TYPE ( 18,30 ) , SM_CODE ( 50,10 ) , SM_CARRIER ( 61,20 ) , SM_CONTRACT ( 82,20 ) ) ) , excessive columns ignored ( ignore_extra_data ) , and headers included ( header ) .
+postgres=# COPY tpcds.ship_mode_t1 FROM ' /home/omm/ds_ship_mode.dat ' FIXED FORMATTER ( SM_SHIP_MODE_SK ( 0 , 2 ) , SM_SHIP_MODE_ID ( 2 , 16 ) , SM_TYPE ( 18 , 30 ) , SM_CODE ( 50 , 10 ) , SM_CARRIER ( 61 , 20 ) , SM_CONTRACT ( 82 , 20 ) ) header ignore_extra_data ;
+
Value range: a SELECT or VALUES command in parentheses
+
+
table_name
+
Specifies the name (possibly schema-qualified) of an existing table.
+
Value range: an existing table name
+
+
column_name
+
Specifies an optional list of columns to be copied.
+
Value range: any columns. All columns will be copied if no column list is specified.
+
+
STDIN
+
Specifies that input comes from the standard input.
+
+
STDOUT
+
Specifies that output goes to the standard output.
+
+
FIXED
+
Fixes column length. When the column length is fixed, DELIMITER, NULL, and CSV cannot be specified. When FIXED is specified, BINARY, CSV, and TEXT cannot be specified by option or copy_option.
+
The definition of fixed length is as follows:
+
The column length of each record is the same.
Spaces are used for column padding. Columns of the numeric type are left-aligned and columns of the string type are right-aligned.
No delimiters are used between columns.
+
+
+
[USING] DELIMITER 'delimiters'
+
The string that separates columns within each row (line) of the file, and it cannot be larger than 10 bytes.
+
Value range: The delimiter cannot include any of the following characters: \.abcdefghijklmnopqrstuvwxyz0123456789
+
The default value is a tab character in text format and a comma in CSV format.
+
+
WITHOUT ESCAPING
+
Specifies, in text format, whether to escape the backslash (\) and its following characters.
+
Value range: text only
+
+
LOG ERRORS
+
If this parameter is specified, the error tolerance mechanism for data type errors in the COPY FROM statement is enabled. Row errors are recorded in the public.pgxc_copy_error_log table in the database for future reference.
+
Value range: a value set while data is imported using COPY FROM.
+
The restrictions of this error tolerance parameter are as follows:
+
This error tolerance mechanism captures only the data type errors (DATA_EXCEPTION) that occur during data parsing of COPY FROM on the primary node of the database.
Before enabling error tolerance for COPY FROM for the first time in a database, check whether the public.pgxc_copy_error_log table exists. If not, call the copy_error_log_create() function to create it. If it does, copy its data elsewhere, delete it, and call the copy_error_log_create() function to create the table. For details about columns in the public.pgxc_copy_error_log table, see Table 1.
While a COPY FROM statement with specified LOG ERRORS is being executed, if public.pgxc_copy_error_log does not exist or does not have the table definitions compliant with those predefined in copy_error_log_create(), an error will be reported. Ensure that the error table is created using the copy_error_log_create() function. Otherwise, COPY FROM statements with error tolerance may fail to be run.
If existing error tolerance parameters (for example, IGNORE_EXTRA_DATA) of the COPY statement are enabled, the error of the corresponding type will be processed as specified by the parameters and no error will be reported. Therefore, the error table does not contain such error data.
+
+
+
LOG ERRORS DATA
+
The differences between LOG ERRORS DATA and LOG ERRORS are as follows:
+
LOG ERRORS DATA fills the rawrecord field in the error tolerance table.
Only users with the super permission can use the LOG ERRORS DATA parameter.
If error content is too complex, it may fail to be written to the error tolerance table by using LOG ERRORS DATA, causing a task failure.
Used with the LOG ERROR parameter to set the upper limit of the tolerated errors in the COPY FROM statement. If the number of errors exceeds the limit, later errors will be reported based on the original mechanism.
+
Value range: a positive integer (1 to INTMAX) or unlimited
+
Default value: If LOG ERRORS is not specified, an error will be reported. If LOG ERRORS is specified, the default value is 0.
+
In the error tolerance mechanism described in the description of LOG ERRORS, the count of REJECT LIMIT is calculated based on the number of data parsing errors on the primary node of the database where the COPY FROM statement is executed, not based on the number of all errors on the primary node.
+
+
+
FORMATTER
+
Defines the place of each column in the data file in fixed length mode. Defines the place of each column in the data file in the column(offset,length) format.
+
Value range:
+
The value of offset must be larger than 0. The unit is byte.
The value of length must be larger than 0. The unit is byte.
+
The total length of all columns must be less than 1 GB.
+
Replace columns that are not in the file with null.
+
+
OPTION { option_name ' value ' }
+
Specifies all types of parameters of a compatible foreign table.
+
FORMAT
Specifies the format of the source data file in the foreign table.
+
Value range: CSV, TEXT, FIXED, and BINARY
+
The CSV file can process newline characters efficiently, but cannot process certain special characters well.
The TEXT file can process certain special characters efficiently, but cannot process newline characters well.
In FIXED files, the column length of each record is the same. Spaces are used for padding, and the excessive part will be truncated.
All data in the BINARY file is stored/read as binary format rather than as text. It is faster than the text and CSV formats, but a binary-format file is less portable.
+
Default value: TEXT
+
DELIMITER
Specifies the character that separates columns within each row (line) of the file.
The value of DELIMITER cannot be \r or \n.
A delimiter cannot be the same as the null value. The delimiter for the CSV format cannot be same as the quote value.
The delimiter for the TEXT format data cannot contain lowercase letters, digits, or special characters (.\).
The data length of a single row should be less than 1 GB. A row that has many columns using long delimiters cannot contain much valid data.
You are advised to use multi-character delimiters or invisible delimiters. For example, you can use multi-characters (such as $^&) and invisible characters (such as 0x07, 0x08, and 0x1b).
+
+
+
Value range: a multi-character delimiter within 10 bytes
+
Default value:
+
A tab character in TEXT format
A comma (,) in CSV format
No delimiter in FIXED format
+
NULL
Specifies the string that represents a null value.
+
Value range:
+
A null value cannot be \r or \n. The maximum length is 100 characters.
A null value cannot be the same as the DELIMITER or QUOTE value.
+
Default value:
+
The default value for the CSV format is an empty string without quotation marks.
The default value for the TEXT format is \N.
+
HEADER
Specifies whether a file contains a header with the names of each column in the file. header is available only for CSV and FIXED files.
+
When data is imported, if header is on, the first row of the data file will be identified as the header and ignored. If header is off, the first row will be identified as a data row.
+
When data is exported, if header is on, fileheader must be specified. If header is off, an exported file does not contain a header.
+
Value range: true/on and false/off
+
Default value: false
+
QUOTE
Specifies a quoted character string for a CSV file.
+
Default value: single quotation marks ('')
+
The value of QUOTE cannot be the same as that of DELIMITER or NULL.
The value of QUOTE must be a single-byte character.
Invisible characters are recommended, such as 0x07, 0x08, and 0x1b.
+
+
ESCAPE
Specifies an escape character for a CSV file. The value must be a single-byte character.
+
Default value: single quotation marks ('') If the value is the same as that of QUOTE, it will be replaced by \0.
+
EOL 'newline_character'
Specifies the newline character style of the imported or exported data file.
+
Value range: multi-character newline characters within 10 bytes Common newline characters include \r (0x0D), \n (0x0A), and \r\n (0x0D0A). Special newline characters include $ and #.
+
The EOL parameter supports only the TEXT format for data import and export and does not support the CSV or FIXED format for data import. For forward compatibility, the EOL parameter can be set to 0x0D or 0x0D0A for data export in the CSV or FIXED format.
The value of EOL cannot be the same as that of DELIMITER or NULL.
The EOL parameter value cannot contain the following characters: .abcdefghijklmnopqrstuvwxyz0123456789.
+
+
FORCE_QUOTE { ( column_name [, ...] ) | * }
Forces quotation marks to be used for all non-null values in each specified column, in CSV COPY TO mode. Null values are not quoted.
+
Value range: an existing column name
+
FORCE_NOT_NULL ( column_name [, ...] )
Assigns a value to a specified column in CSV COPY FROM mode.
+
Value range: an existing column name
+
ENCODING
Specifies that the file is encoded in the encoding_name. If this option is omitted, the current encoding format is used by default.
+
IGNORE_EXTRA_DATA
Specifies whether to ignore excessive columns when the number of data source files exceeds the number of foreign table columns. This parameter is used only during data import.
+
Value range: true/on and false/off
+
true/on: If the number of columns in a data source file is greater than that defined by the foreign table, the extra columns at the end of a row are ignored.
false/off: If the number of columns in a data source file is greater than that defined by the foreign table, the following error message is reported:
extra data after last expected column
+
+
Default value: false
+
If a newline character at the end of a row is missing and the row and another row are integrated into one, data in another row is ignored after the parameter is set to true.
+
+
COMPATIBLE_ILLEGAL_CHARS
Specifies whether to tolerate invalid characters during data import. The parameter is valid only for data import using COPY FROM.
+
Value range: true/on and false/off
+
true/on: No error message is reported and data import is not interrupted when there are invalid characters. Invalid characters are converted into valid ones, and then imported to the database.
false/off: An error occurs when there are invalid characters, and the import stops.
+
Default value: false/off
+
The rules for converting invalid characters are as follows:
+
1. \0 is converted to a space.
+
2. Other invalid characters are converted to question marks.
+
3. When compatible_illegal_chars is set to true/on, after invalid characters such as NULL, DELIMITER, QUOTE, and ESCAPE are converted to spaces or question marks, an error message stating "illegal chars conversion may confuse COPY escape 0x20" will be displayed to remind you of possible parameter confusion caused by the conversion.
+
+
FILL_MISSING_FIELDS
Specifies how to handle the problem that the last column of a row in a source data file is lost during data import.
+
Value range: true/on and false/off
+
Default value: false/off
+
DATE_FORMAT
Specifies the DATE format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
You can use the TIMESTAMP_FORMAT parameter to set the DATE format to TIMESTAMP for data import. For details, see TIMESTAMP_FORMAT below.
+
+
TIME_FORMAT
Specifies the TIME format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
Specifies the TIMESTAMP format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
Specifies the SMALLDATETIME format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
Specifies the string that represents a null value.
When using COPY FROM, any data item that matches this string will be stored as a null value, so make sure that you use the same string as you used with COPY TO.
+
+
+
Value range:
+
A null value cannot be \r or \n. The maximum length is 100 characters.
A null value cannot be the same as the DELIMITER or QUOTE value.
+
Default value:
+
The default value for the TEXT format is \N.
The default value for the CSV format is an empty string without quotation marks.
+
HEADER
Specifies whether a file contains a header with the names of each column in the file. header is available only for CSV and FIXED files.
+
When data is imported, if header is on, the first row of the data file will be identified as the header and ignored. If header is off, the first row will be identified as a data row.
+
When data is exported, if header is on, fileheader must be specified. If header is off, an exported file does not contain a header.
+
FILEHEADER
Specifies a file that defines the content in the header for exported data. The file contains data description of each column.
+
This parameter is available only when header is on or true.
fileheader specifies an absolute path.
The file can contain only one row of header information, and ends with a newline character. Excess rows will be discarded. (Header information cannot contain newline characters.)
The length of the file including the newline character cannot exceed 1 MB.
+
+
FREEZE
Sets the COPY loaded data row as frozen, like these data have executed VACUUM FREEZE.
+
This is a performance option of initial data loading. The data will be frozen only when the following three requirements are met:
+
The table being loaded has been created or truncated in the current subtransaction before copying.
There are no cursors open in the current transaction.
There are no original snapshots in the current transaction.
+
When COPY is completed, all the other sessions will see the data immediately. However, this violates the general principle of MVCC visibility, and users should understand that this may cause potential risks.
+
+
FORCE NOT NULL column_name [, ...]
In CSV COPY FROM mode, the specified column is not null. If the column is null, its value is regarded as a string of 0 characters.
+
Value range: an existing column name
+
FORCE QUOTE { column_name [, ...] | * }
Forces quotation marks to be used for all non-null values in each specified column, in CSV COPY TO mode. Null values are not quoted.
+
Value range: an existing column name
+
BINARY
Specifies that data is stored and read in binary mode instead of text mode. In binary mode, you cannot declare DELIMITER, NULL, or CSV. When BINARY is specified, CSV, FIXED, and TEXT cannot be specified through option or copy_option.
+
CSV
Enables the CSV mode. When CSV is specified, BINARY, FIXED, and TEXT cannot be specified through option or copy_option.
+
QUOTE [AS] 'quote_character'
Specifies a quoted character string for a CSV file.
+
Default value: single quotation marks ('')
+
The value of QUOTE cannot be the same as that of DELIMITER or NULL.
The value of QUOTE must be a single-byte character.
Invisible characters are recommended, such as 0x07, 0x08, and 0x1b.
+
+
ESCAPE [AS] 'escape_character'
Specifies an escape character for a CSV file. The value must be a single-byte character.
+
The default value is single quotation marks (''). If the value is the same as that of QUOTE, it will be replaced by \0.
+
EOL 'newline_character'
Specifies the newline character style of the imported or exported data file.
+
Value range: multi-character newline characters within 10 bytes Common newline characters include \r (0x0D), \n (0x0A), and \r\n (0x0D0A). Special newline characters include $ and #.
+
The EOL parameter supports only the TEXT format for data import and export and does not support the CSV or FIXED format. For forward compatibility, the EOL parameter can be set to 0x0D or 0x0D0A for data export in the CSV or FIXED format.
The value of EOL cannot be the same as that of DELIMITER or NULL.
The EOL parameter value cannot contain the following characters: .abcdefghijklmnopqrstuvwxyz0123456789.
+
+
ENCODING 'encoding_name'
Specifies the name of a file encoding format.
+
Value range: a valid encoding format
+
Default value: current encoding format
+
IGNORE_EXTRA_DATA
If the number of columns in a data source file is greater than that defined by the foreign table, the extra columns at the end of a row are ignored. This parameter is used only during data import.
+
If this parameter is not used and the number of columns in the data source file is greater than that defined in the foreign table, the following error information is displayed:
extra data after last expected column
+
+
COMPATIBLE_ILLEGAL_CHARS
Specifies that invalid characters are tolerated during data import. Invalid characters are converted and then imported to the database. No error is reported and the import is not interrupted. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
+
If this parameter is not used, an error is reported when invalid characters are encountered during the import, and the import is interrupted.
+
The rules for converting invalid characters are as follows:
+
1. \0 is converted to a space.
+
2. Other invalid characters are converted to question marks.
+
3. When compatible_illegal_chars is set to true/on, after invalid characters such as NULL, DELIMITER, QUOTE, and ESCAPE are converted to spaces or question marks, an error message stating "illegal chars conversion may confuse COPY escape 0x20" will be displayed to remind you of possible parameter confusion caused by the conversion.
+
+
FILL_MISSING_FIELDS
Specifies how to handle the problem that the last column of a row in a source data file is lost during data import.
+
Value range: true/on and false/off
+
Default value: false/off
+
Do not specify this option. Currently, it does not enable error tolerance, but will make the parser ignore the said errors during data parsing on the primary node of the database. Such errors will not be recorded in the COPY error table (enabled using LOG ERRORS REJECT LIMIT) but will be reported later by the database node. Therefore, do not specify this option.
+
+
DATE_FORMAT 'date_format_string'
Specifies the DATE format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
You can use the TIMESTAMP_FORMAT parameter to set the DATE format to TIMESTAMP for data import. For details, see TIMESTAMP_FORMAT below.
+
+
TIME_FORMAT 'time_format_string'
Specifies the TIME format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
Specifies the TIMESTAMP format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
Specifies the SMALLDATETIME format for data import. The BINARY format is not supported. When data of such format is imported, error "cannot specify bulkload compatibility options in BINARY mode" will occur. The parameter is valid only for data import using COPY FROM.
The following special backslash sequences are recognized by COPY FROM:
\b: Backslash (ASCII 8)
\f: Form feed (ASCII 12)
\n: Newline character (ASCII 10)
\r: Carriage return character (ASCII 13)
\t: Tab (ASCII 9)
\v: Vertical tab (ASCII 11)
\digits: Backslash followed by one to three octal digits specifies that the ASCII value is the character with that numeric code.
\xdigits: Backslash followed by an x and one or two hex digits specifies the character with that numeric code.
+
+
]]>
+
+
+
Function
+
Create a database. By default, a new database is created by copying the standard system database template0. Only template0 can be used to create a new database.
+
+
Precautions
+
A user that has the CREATEDB permission or a system administrator can create a database.
CREATE DATABASE cannot be executed inside a transaction block.
Errors along the line of "could not initialize database directory" are most likely related to insufficient permissions on the data directory, a full disk, or other file system problems.
+
+
Examples
+
-- Create database music using GBK ( the local encoding type is also GBK ) :
+postgres=# CREATE DATABASE music ENCODING ' GBK ' template = template0 ;
+
+-- Create database music2 and specify user jim as its owner:
+postgres=# CREATE DATABASE music2 OWNER jim ;
+
+-- Create database music3 using template template0 and specify user jim as its owner:
+postgres=# CREATE DATABASE music3 OWNER jim TEMPLATE template0 ;
+
+-- Create a database compatible with the TD format.
+postgres=# CREATE DATABASE td_compatible_db DBCOMPATIBILITY ' C ' ;
+
+-- Create a database compatible with the ORA format.
+postgres=# CREATE DATABASE ora_compatible_db DBCOMPATIBILITY ' A ' ;
+
Value range: a string. It must comply with the naming convention.
+
+
OWNER [ = ] user_name
+
Specifies the owner of the new database. By default, the owner of a new database is the current user.
+
Value range: an existing username
+
+
TEMPLATE [ = ] template
+
Specifies a template name. That is, the template from which the database is created. openGauss creates a database by copying data from a template database. openGauss has two default template databases template0 and template1 and a default user database postgres.
+
Value range: template0.
+
+
ENCODING [ = ] encoding
+
Specifies the encoding format used by the new database. The value can be a string (for example, SQL_ASCII) or an integer.
+
By default, the encoding format of the template database is used. The encoding formats of the template databases template0 and template1 depend on the OS. The encoding format of template1 cannot be changed. If you need to change the encoding format when creating a database, use template0.
+
Common values : GBK, UTF8, and Latin1
+
The character set encoding of the new database must be compatible with the local settings (LC_COLLATE and LC_CTYPE).
When the specified character encoding set is GBK, some uncommon Chinese characters cannot be directly used as object names. This is because the byte encoding overlaps with the ASCII characters @A-Z[\]^_`a-z{|} when the second byte of the GBK ranges from 0x40 to 0x7E. @[\]^_'{|} is an operator in the database. If it is directly used as an object name, a syntax error will be reported. For example, the GBK hexadecimal code is 0x8240, and the second byte is 0x40, which is the same as the ASCII character @. Therefore, the character cannot be used as an object name. If you do need to use this function, you can add double quotation marks ("") to avoid this problem when creating and accessing objects.
+
+
+
LC_COLLATE [ = ] lc_collate
+
Specifies the character set used by the new database. For example, set this parameter by using lc_collate = 'zh_CN.gbk'.
+
The use of this parameter affects the sort order of strings (for example, the order of using ORDER BY for execution and the order of using indexes on text columns). By default, the sorting order of the template database is used.
+
Value range: a valid sorting type
+
+
LC_CTYPE [ = ] lc_ctype
+
Specifies the character class used by the new database. For example, set this parameter by using lc_ctype = 'zh_CN.gbk'. The use of this parameter affects the classification of characters, such as uppercase letters, lowercase letters, and digits. By default, the character classification of the template database is used.
Value range: A, B, and C , indicating O, MY, and TD databases, respectively.
+
+
TABLESPACE [ = ] tablespace_name
+
Specifies the tablespace of the database.
+
Value range: an existing tablespace name
+
+
CONNECTION LIMIT [ = ] connlimit
+
Specifies the maximum number of concurrent connections that can be made to the new database.
+
The system administrator is not restricted by this parameter.
connlimit is calculated separately for each master database node. Number of connections of the openGauss = connlimit x Number of normal CN master database nodes.
+
+
Value range: an integer greater than or equal to -1 The default value is -1, indicating that there is no limit.
+
]]>
+
+
+
Function
+
CREATE DATA SOURCE creates an external data source, which defines the information about the database that openGauss will connect to.
+
+
Precautions
+
The data source name must be unique in the database and comply with the identifier naming rules. Its length cannot exceed 63 bytes. Otherwise, it will be truncated.
Only the system administrator or initial user has the permission to create data sources. The user who creates the object is the default owner of the object.
If the password option is displayed, ensure that the datasource.key.cipher and datasource.key.rand files exist in the $GAUSSHOME/bin directory of each node in openGauss. If the two files do not exist, use the gs_guc tool to generate them and use the gs_ssh tool to release them to the $GAUSSHOME/bin directory on each node in openGauss.
+
+
Examples
+
-- Create an empty data source that does not contain any information.
+postgres=# CREATE DATA SOURCE ds_test1 ;
+
+-- Create a data source with TYPE information and VERSION being null.
+postgres=# CREATE DATA SOURCE ds_test2 TYPE ' MPPDB ' VERSION NULL ;
+
+-- Create a data source that contains only OPTIONS.
+postgres=# CREATE DATA SOURCE ds_test3 OPTIONS ( dsn ' openGauss ' , encoding ' utf8 ' ) ;
+
+-- Create a data source that contains TYPE, VERSION, and OPTIONS.
+postgres=# CREATE DATA SOURCE ds_test4 TYPE ' unknown ' VERSION ' 11.2.3 ' OPTIONS ( dsn ' openGauss ' , username ' userid ' , password ' pwd@123456 ' , encoding ' ' ) ;
+
Specifies the name of the new data source, which must be unique in the database.
+
Value range: a string. It must comply with the naming convention rule.
+
+
TYPE
+
Specifies the type of the data source. This parameter can be left empty, and its default value will be used.
+
Value range: an empty string or a non-empty string
+
+
VERSION
+
Specifies the version number of the new data source. This parameter can be left empty or set to null.
+
Value range: an empty string, a non-empty string, or null
+
+
OPTIONS
+
Specifies the options of the data source. This parameter can be left empty or specified using the following keywords:
optname
Specifies the option name.
+
Value range: dsn, username, password, and encoding. The value is case-insensitive.
+
dsn corresponds to the DSN in the ODBC configuration file.
username/password indicates the username and password for connecting to the destination database.
The user name and password entered by the user are encrypted in the openGauss background to ensure security. The key file required for encryption must be generated using the gs_guc tool and released to the $GAUSSHOME/bin directory of each node in openGauss using the gs_ssh tool. The user name and password cannot contain the prefix "encryptOpt". Otherwise, they are considered as encrypted ciphertext.
+
encoding indicates the character string encoding mode used for interaction with the destination database (including the sent SQL statements and returned data of the character type). Its validity is not checked during object creation. Whether data can be encoded and decoded depends on whether the encoding you specified can be used in the database.
+
optvalue
Specifies the option value.
+
Value range: an empty string or a non-empty string
+
+
+
]]>
+
+
+
Function
+
CREATE DIRECTORY creates a directory. The directory defines an alias for a path in the server file system and is used to store data files used by users.
+
+
Precautions
+
By default, only initial users can create directories. If enable_access_server_directory is enabled (for details, see enable_access_server_directory), users with the sysadmin permission can also create directories.
By default, the user who creates a directory has the read and write permissions on the directory.
The default owner of a directory is the user who creates the directory.
A directory cannot be created for the following paths:
The path contains special characters.
The path is a relative path.
The path is a symbolic link.
+
The following validity check is performed during directory creation:
Check whether the path exists in the OS. If it does not exist, a message is displayed, indicating the potential risks.
Check whether the database initial user omm has the R/W/X permissions for the OS path. If the user does not have all the permissions, a message is displayed, indicating the potential risks.
+
In openGauss, ensure that the path is the same on all the nodes. Otherwise, the path may fail to be found on some nodes when the directory is used.
+
+
Examples
+
-- Create a directory.
+postgres=# CREATE OR REPLACE DIRECTORY dir as ' /tmp/ ' ;
+
Value range: a string. It must comply with the naming convention rule.
+
+
path_name
+
Specifies the OS path for which a directory is to be created.
+
Value range: a valid OS path
+
]]>
+
+
+
Function
+
CREATE FUNCTION creates a function.
+
+
Precautions
+
If the parameters or return values of a function have precision, the precision is not checked.
When creating a function, you are advised to explicitly specify the schemas of tables in the function definition. Otherwise, the function may fail to be executed.
current_schema and search_path specified by SET during function creation are invalid. search_path and current_schema before and after function execution should be the same.
If a function has output parameters, the SELECT statement uses the default values of the output parameters when calling the function. When the CALL statement calls the function, it requires that the output parameters must be specified. When the CALL statement calls an overloaded PACKAGE function, it can use the default values of the output parameters. For details, see examples in CALL.
Only the functions compatible with PostgreSQL or those with the PACKAGE attribute can be overloaded. After REPLACE is specified, a new function is created instead of replacing a function if the number of parameters, parameter type, or return value is different.
You can use the SELECT statement to specify different parameters using identical functions, but cannot use the CALL statement to call identical functions without the PACKAGE attribute.
When you create a function, you cannot insert other agg functions out of the avg function or other functions.
By default, the permissions to execute new functions are granted to PUBLIC. For details, see GRANT. You can revoke the default execution permissions from PUBLIC and grant them to other users as needed. To avoid the time window during which new functions can be accessed by all users, create functions in transactions and set function execution permissions.
+
+
Examples
+
-- Define a function as SQL query.
+postgres=# CREATE FUNCTION func_add_sql ( integer , integer ) RETURNS integer
+AS ' select $1 + $2 ; '
+LANGUAGE SQL
+IMMUTABLE
+RETURNS NULL ON NULL INPUT ;
+
+-- Add an integer by parameter name using PL/pgSQL.
+postgres=# CREATE OR REPLACE FUNCTION func_increment_plsql ( i integer ) RETURNS integer AS $$
+BEGIN
+RETURN i + 1 ;
+END ;
+$$ LANGUAGE plpgsql ;
+
+-- Return the RECORD type.
+CREATE OR REPLACE FUNCTION compute ( i int , out result_1 bigint , out result_2 bigint )
+returns SETOF RECORD
+as $$
+begin
+result_1 = i + 1 ;
+result_2 = i * 10 ;
+return next;
+end ;
+$$language plpgsql ;
+
+-- Return a record containing multiple output parameters.
+postgres=# CREATE FUNCTION func_dup_sql ( in int , out f1 int , out f2 text )
+AS $$ SELECT $1 , CAST ( $1 AS text ) || ' is text ' $$
+LANGUAGE SQL ;
+postgres=# SELECT * FROM func_dup_sql ( 42 ) ;
+
+-- Compute the sum of two integers and return the result ( if the input is null, the returned result is null ) .
+postgres=# CREATE FUNCTION func_add_sql2 ( num1 integer , num2 integer ) RETURN integer
+AS
+BEGIN
+RETURN num1 + num2 ;
+END ;
+/
+
+
Syntax
+
Syntax (compatible with PostgreSQL) for creating a customized function:
Specifies the name of the function to create (optionally schema-qualified).
+
Value range: a string. It must comply with the naming convention.
+
+
argname
+
Specifies the parameter name of the function.
+
Value range: a string. It must comply with the naming convention.
+
+
argmode
+
Specifies the parameter mode of the function.
+
Value range: IN, OUT, INOUT, and VARIADIC. The default value is IN. Only the parameter of the OUT mode can be followed by VARIADIC. The parameters of OUT and INOUT cannot be used in the function definition of RETURNS TABLE.
+
VARIADIC specifies parameters of the array type.
+
+
+
argtype
+
Specifies the data type of a function parameter.
+
+
expression
+
Specifies the default expression of a parameter.
+
+
rettype
+
Specifies the return data type.
+
When there is OUT or INOUT parameter, the RETURNS clause can be omitted. If the clause exists, the result type of the clause must be the same as that of the output parameter. If there are multiple output parameters, the result type of the clause is RECORD. Otherwise, the result type of the clause is the same as that of a single output parameter.
+
The SETOF modifier indicates that the function will return a set of items, rather than a single item.
+
+
column_name
+
Specifies the column name.
+
+
column_type
+
Specifies the column type.
+
+
definition
+
Specifies a string constant defining a function. Its meaning depends on the language. It can be an internal function name, a path pointing to a target file, a SQL query, or text in a procedural language.
+
+
LANGUAGE lang_name
+
Specifies the name of the language that is used to implement the function. It can be SQL, internal, or the name of a customized process language. To ensure downward compatibility, the name can use single quotation marks. Contents in single quotation marks must be capitalized.
+
+
WINDOW
+
Indicates that this function is a window function. The WINDOW attribute cannot be changed when replacing an existing function definition.
+
For a customized window function, the value of LANGUAGE can only be internal, and the referenced internal function must be a window function.
+
+
+
IMMUTABLE
+
Specifies that the function always returns the same result if the parameter values are the same.
+
+
STABLE
+
Specifies that the function cannot modify the database, and that within a single table scan it will consistently return the same result for the same parameter value, but its result varies by SQL statements.
+
+
VOLATILE
+
Specifies that the function value can change in a single table scan and no optimization is performed.
+
+
PACKAGE
+
Specifies whether the function can be overloaded. PostgreSQL-style functions can be overloaded, and this parameter is designed for functions of other styles.
All PACKAGE and non-PACKAGE functions cannot be overloaded or replaced.
PACKAGE functions do not support parameters of the VARIADIC type.
The PACKAGE attribute of functions cannot be modified.
+
+
+
LEAKPROOF
+
Specifies that the function has no side effects. LEAKPROOF can be set only by the system administrator.
+
+
CALLED ON NULL INPUT
+
Declares that some parameters of the function can be invoked in normal mode if the parameter values are null. This parameter can be omitted.
+
+
RETURNS NULL ON NULL INPUT
+
STRICT
+
Specifies that the function always returns null whenever any of its parameters is null. If this parameter is specified, the function is not executed when there are null parameters; instead a null result is returned automatically.
+
RETURNS NULL ON NULL INPUT and STRICT have the same functions.
+
+
EXTERNAL
+
The keyword EXTERNAL is allowed for SQL conformance, but it is optional since, unlike in SQL, this feature applies to all functions not only external ones.
+
+
SECURITY INVOKER
+
AUTHID CURRENT_USER
+
Specifies that the function will be executed with the permissions of the user who invokes it. This parameter can be omitted.
+
SECURITY INVOKER and AUTHID CURRENT_USER have the same functions.
+
+
SECURITY DEFINER
+
AUTHID DEFINER
+
Specifies that the function will be executed with the permissions of the user who created it.
+
AUTHID DEFINER and SECURITY DEFINER have the same functions.
+
+
COST execution_cost
+
Estimates the execution cost of a function.
+
The unit of execution_cost is cpu_operator_cost.
+
Value range: a positive integer
+
+
ROWS result_rows
+
Estimates the number of rows returned by the function. This is only allowed when the function is declared to return a set.
+
Value range: a positive number. The default value is 1000.
+
+
configuration_parameter
+
value
Sets a specified database session parameter to a specified value. If the value is DEFAULT or RESET, the default setting is used in the new session. OFF closes the setting.
+
Value range: a string
+
DEFAULT
OFF
RESET
+
Specifies the default value.
+
from current
Uses the value of configuration_parameter of the current session.
+
+
+
plsql_body
+
Specifies the PL/SQL stored procedure body.
+
When a user is created in the function body, the plaintext password is recorded in the log. You are not advised to do it.
+
+
]]>
+
+
+
Function
+
CREATE GROUP creates a user group.
+
+
Precautions
+
CREATE GROUP is an alias for CREATE ROLE, and it is not a standard SQL syntax and not recommended. Users can use CREATE ROLE directly.
+
+
Syntax
+
CREATE GROUP group_name [ [ WITH ] option [ ... ] ] [ ENCRYPTED | UNENCRYPTED ] { PASSWORD | IDENTIFIED BY } { 'password' | DISABLE };
CREATE INDEX creates an index in a specified table.
+
Indexes are primarily used to enhance database performance (though inappropriate use can result in database performance deterioration). You are advised to create indexes on:
+
Columns that are often queried
Join conditions. For a query on joined columns, you are advised to create a composite index on the columns, for example, select * from t1 join t2 on t1.a=t2.a and t1.b=t2.b. You can create a composite index on columns a and b in table t1.
Columns having filter criteria (especially scope criteria) of a where clause
Columns that appear after order by, group by, and distinct
+
Partitioned tables do not support concurrent index creation, partial index creation, and NULL FIRST.
+
+
Precautions
+
Indexes consume storage and computing resources. Creating too many indexes has negative impact on database performance (especially the performance of data import. Therefore, you are advised to import the data before creating indexes). Therefore, create indexes only when they are necessary.
All functions and operators used in an index definition must be immutable, that is, their results must depend only on their parameters and never on any outside influence (such as the contents of another table or the current time). This restriction ensures that the behavior of the index is well-defined. To use a customized function in an index expression or WHERE clause, remember to mark the function immutable when you create it.
A unique index created on a partitioned table must include a partitioned column and all the partition keys.
Column-store tables support B-tree and psort indexes. If the two indexes are used, you cannot create expression, partial, and unique indexes.
Column-store tables support GIN indexes, rather than partial indexes and unique indexes. If GIN indexes are used, you can create expression indexes. However, an expression in this situation cannot contain empty splitters, empty columns, or multiple columns.
+
+
Examples
+
-- Create a common index on the SM_SHIP_MODE_SK column in the tpcds.ship_mode_t1 table.
+postgres=# CREATE UNIQUE INDEX ds_ship_mode_t1_index1 ON tpcds.ship_mode_t1 ( SM_SHIP_MODE_SK ) ;
+
+-- Create a B-tree index on the SM_SHIP_MODE_SK column in the tpcds.ship_mode_t1 table.
+postgres=# CREATE INDEX ds_ship_mode_t1_index4 ON tpcds.ship_mode_t1 USING btree ( SM_SHIP_MODE_SK ) ;
+
+-- Create an expression index on the SM_CODE column in the tpcds.ship_mode_t1 table:
+postgres=# CREATE INDEX ds_ship_mode_t1_index2 ON tpcds.ship_mode_t1 ( SUBSTR ( SM_CODE , 1 , 4 ) ) ;
+
+-- Create a partial index on the SM_SHIP_MODE_SK column where SM_SHIP_MODE_SK is greater than 10 in the tpcds.ship_mode_t1 table.
+postgres=# CREATE UNIQUE INDEX ds_ship_mode_t1_index3 ON tpcds.ship_mode_t1 ( SM_SHIP_MODE_SK ) WHERE SM_SHIP_MODE_SK>10 ;
+
+-- Create the partitioned table index ds_customer_address_p1_index1 without specifying the index partition name.
+postgres=# CREATE INDEX ds_customer_address_p1_index1 ON tpcds.customer_address_p1 ( CA_ADDRESS_SK ) LOCAL ;
+
+-- Create the partitioned table index ds_customer_address_p1_index2 with the name of the index partition specified.
+postgres=# CREATE INDEX ds_customer_address_p1_index2 ON tpcds.customer_address_p1 ( CA_ADDRESS_SK ) LOCAL
+ (
+PARTITION CA_ADDRESS_SK_index1 ,
+PARTITION CA_ADDRESS_SK_index2 TABLESPACE example3 ,
+PARTITION CA_ADDRESS_SK_index3 TABLESPACE example4
+ )
+TABLESPACE example2 ;
+
+-- Create a column-store table and its GIN index:
+postgres=# create table cgin_create_test ( a int , b text ) with ( orientation = column ) ;
+CREATE TABLE
+postgres=# create index cgin_test on cgin_create_test using gin ( to_tsvector ( ' ngram ' , b ) ) ;
+CREATE INDEX
+
+
Syntax
+
Create an index on a table.
CREATE [ UNIQUE ] INDEX [ [schemaname.]index_name ] ON table_name [ USING method ]
+ ({ { column_name | ( expression ) } [ COLLATE collation ] [ opclass ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] }[, ...] )
+ [ WITH ( {storage_parameter = value} [, ... ] ) ]
+ [ TABLESPACE tablespace_name ]
+ [ WHERE predicate ];
Creates a unique index. In this way, the system checks whether new values are unique in the index column. Attempts to insert or update data which would result in duplicate entries will generate an error.
+
Currently, only B-tree supports UNIQUE indexes.
+
+
schema_name
+
Specifies the schema name.
+
Value range: an existing schema name
+
+
index_name
+
Specifies the name of the index to create. No schema name can be included here; the index is always created in the same schema as its parent table.
+
Value range: a string. It must comply with the naming convention.
+
+
table_name
+
Specifies the name of the table to be indexed (optionally schema-qualified).
+
Value range: an existing table name
+
+
USING method
+
Specifies the name of the index method to be used.
+
Value range:
+
btree: B-tree indexes store key values of data in a B+ tree structure. This structure helps users to quickly search for indexes. B-tree supports comparison queries with a scope specified.
gin: GIN indexes are reverse indexes and can process values that contain multiple keys (for example, arrays).
gist: GiST indexes are suitable for the set data type and multidimensional data types, such as geometric and geographic data types.
Psort: psort index. It is used to perform partial sort on column-store tables.
+
Row-store tables support the following index types: btree (default), gin, and gist. Column-store tables support the following index types: Psort (default), btree, and gin.
+
Column-store tables support GIN indexes only for the tsvector type. That is, the input parameter for creating a column-store GIN index must be the return value of the to_tsvector function. This method is commonly used for GIN indexes.
+
+
+
column_name
+
Specifies the name of the column on which an index is to be created.
+
Multiple columns can be specified if the index method supports multi-column indexes. A maximum of 32 columns can be specified.
+
+
expression
+
Specifies an expression based on one or more columns of the table. The expression usually must be written with surrounding parentheses, as shown in the syntax. However, the parentheses can be omitted if the expression has the form of a function call.
+
Expression can be used to obtain fast access to data based on some transformation of the basic data. For example, an index computed on upper(col) would allow the clause WHERE upper(col) = 'JIM' to use an index.
+
If an expression contains IS NULL, the index for this expression is invalid. In this case, you are advised to create a partial index.
+
+
COLLATE collation
+
Assigns a collation to the column (which must be of a collatable data type). If no collation is specified, the default collation is used.
+
+
opclass
+
Specifies the name of an operator class. An operator class can be specified for each column of an index. The operator class identifies the operators to be used by the index for that column. For example, a B-tree index on the type int4 would use the int4_ops class; this operator class includes comparison functions for values of type int4. In practice, the default operator class for the column's data type is sufficient. The operator class applies to data with multiple sorts. For example, users might want to sort a complex-number data type either by absolute value or by real part. They could do this by defining two operator classes for the data type and then selecting the proper class when making an index.
+
+
ASC
+
Specifies an ascending (default) sort order.
+
+
DESC
+
Specifies a descending sort order.
+
+
NULLS FIRST
+
Specifies that null values appear before non-null values in the sort ordering. This is the default when DESC is specified.
+
+
NULLS LAST
+
Specifies that null values appear after non-null values in the sort ordering. This is the default when DESC is not specified.
+
+
WITH ( {storage_parameter = value} [, ... ] )
+
Specifies the storage parameter used for an index.
+
Value range:
+
Only index GIN supports parameters FASTUPDATE and GIN_PENDING_LIST_LIMIT. Indexes other than GIN and psort support the FILLFACTOR parameter.
FILLFACTOR
The fill factor of an index is a percentage from 10 to 100.
+
Value range: 10鈥?00
+
FASTUPDATE
Specifies whether fast update is enabled for the GIN index.
+
Value range: : ON and OFF
+
Default value: ON
+
GIN_PENDING_LIST_LIMIT
Specifies the maximum capacity of the pending list of the GIN index when fast update is enabled for the GIN index.
+
Value range: 64鈥?em id="EN-US_TOPIC_0242370570__i871914919397">INT_MAX. The unit is KB.
+
Default value: The default value of gin_pending_list_limit depends on gin_pending_list_limit specified in GUC parameters. By default, the value is 4.
+
+
+
+
TABLESPACE tablespace_name
+
Specifies the tablespace for an index. If no tablespace is specified, the default tablespace is used.
+
Value range: an existing table name
+
+
WHERE predicate
+
Creates a partial index. A partial index is an index that contains entries for only a portion of a table, usually a portion that is more useful for indexing than the rest of the table. For example, if you have a table that contains both billed and unbilled orders where the unbilled orders take up a small fraction of the total table and yet that is an often used portion, you can improve performance by creating an index on just that portion. In addition, WHERE with UNIQUE can be used to enforce uniqueness over a subset for a table.
+
Value range: The predicate expression can only refer to columns of the underlying table, but it can use all columns, not just the ones being indexed. Currently, subqueries and aggregate expressions are forbidden in WHERE.
+
+
PARTITION index_partition_name
+
Specifies the name of an index partition.
+
Value range: a string. It must comply with the naming convention.
+
+
TABLESPACE index_partition_tablespace
+
Specifies the tablespace of an index partition.
+
Value range: If this parameter is not specified, the value of index_tablespace is used.
+
]]>
+
+
+
Function
+
CREATE ROW LEVEL SECURITY POLICY creates a row-level access control policy for a table.
+
The policy takes effect only after row-level access control is enabled (by running ALTER TABLE... ENABLE ROW LEVEL SECURITY). Otherwise, this statement does not take effect.
+
Currently, row-level access control affects the read (SELECT, UPDATE, DELETE) of data tables and does not affect the write (INSERT and MERGE INTO) of data tables. The table owner or system administrators can create an expression in the USING clause. When the client reads the data table, the database server combines the expressions that meet the condition and applies it to the execution plan in the statement rewriting phase of a query. For each tuple in a data table, if the expression returns TRUE, the tuple is visible to the current user; if the expression returns FALSE or NULL, the tuple is invisible to the current user.
+
A row-level access control policy name is specific to a table. A data table cannot have row-level access control policies with the same name. Different data tables can have the same row-level access control policy.
+
Row-level access control policies can be applied to specified operations (SELECT, UPDATE, DELETE, and ALL). ALL indicates that SELECT, UPDATE, and DELETE will be affected. For a new row-level access control policy, the default value ALL will be used if you do not specify the operations that will be affected.
+
Row-level access control policies can be applied to a specified user (role) or to all users (PUBLIC). For a new row-level access control policy, the default value PUBLIC will be used if you do not specify the user that will be affected.
+
+
Precautions
+
Row-level access control policies can be defined for row-store tables, row-store partitioned tables, column-store tables, column-store partitioned tables, replication tables, unlogged tables, and hash tables.
Row-level access control policies cannot be defined for foreign tables and temporary tables.
Row-level access control policies cannot be defined for views.
A maximum of 100 row-level access control policies can be defined for a table.
System administrators are not affected by row-level access control policies and can view all data in a table.
Tables queried by using SQL statements, views, functions, and stored procedures are affected by row-level access control policies.
+
+
Syntax
+
CREATE [ ROW LEVEL SECURITY ] POLICY policy_name ON table_name
+ [ AS { PERMISSIVE | RESTRICTIVE } ]
+ [ FOR { ALL | SELECT | INSERT | UPDATE | DELETE } ]
+ [ TO { role_name | PUBLIC | CURRENT_USER | SESSION_USER } [, ...] ]
+ USING ( using_expression )
+
+
Parameter Description
+
+
policy_name
+
Specifies the name of a row-level access control policy to be created. The names of row-level access control policies for a table must be unique.
+
+
table_name
+
Specifies the name of a table to which a row-level access control policy is applied.
+
+
command
+
Specifies the SQL operations affected by a row-level access control policy, including ALL, SELECT, UPDATE, and DELETE. If this parameter is not specified, the default value ALL will be used, covering SELECT, UPDATE, and DELETE.
+
If command is set to SELECT, only tuple data that meets the condition (the return value of using_expression is TRUE) can be queried. The operations that are affected include SELECT, UPDATE.... RETURNING, and DELETE... RETURNING.
+
If command is set to UPDATE, only tuple data that meets the condition (the return value of using_expression is TRUE) can be updated. The operations that are affected include UPDATE, UPDATE ... RETURNING, and SELECT ... FOR UPDATE/SHARE.
+
If command is set to DELETE, only tuple data that meets the condition (the return value of using_expression is TRUE) can be deleted. The operations that are affected include DELETE and DELETE ... RETURNING.
+
The following table describes the relationship between row-level access control policies and SQL statements.
+
+
Table 1 Relationship between row-level access control policies and SQL statements
Command
+
+
SELECT/ALL policy
+
+
UPDATE/ALL policy
+
+
DELETE/ALL policy
+
+
+
+
SELECT
+
+
Existing row
+
+
No
+
+
No
+
+
+
SELECT FOR UPDATE/SHARE
+
+
Existing row
+
+
Existing row
+
+
No
+
+
+
UPDATE
+
+
No
+
+
Existing row
+
+
No
+
+
+
UPDATE RETURNING
+
+
Existing row
+
+
Existing row
+
+
No
+
+
+
DELETE
+
+
No
+
+
No
+
+
Existing row
+
+
+
DELETE RETURNING
+
+
Existing row
+
+
No
+
+
Existing row
+
+
+
+
+
+
+
role_name
+
Specifies database users affected by a row-level access control policy.
+
If this parameter is not specified, the default value PUBLIC will be used, indicating that all database users will be affected. You can specify multiple affected database users.
+
System administrators are not affected by row access control.
+
+
]]>
+
+
+
Function
+
CREATE PROCEDURE creates a stored procedure.
+
+
Precautions
+
If the parameters or return values of a stored procedure have precision, the precision is not checked.
When creating a stored procedure, you are advised to explicitly specify the schemas of all operations on table objects in the stored procedure definition. Otherwise, the stored procedure may fail to be executed.
current_schema and search_path specified by SET during stored procedure creation are invalid. search_path and current_schema before and after function execution should be the same.
If a stored procedure has output parameters, the SELECT statement uses the default values of the output parameters when calling the procedure. When the CALL statement calls the stored procedure or a non-overloaded function, output parameters must be specified. When the CALL statement calls an overloaded PACKAGE function, it can use the default values of the output parameters. For details, see examples in CALL.
A stored procedure with the PACKAGE attribute can use overloaded functions.
When you create a procedure, you cannot insert aggregate functions or other functions out of the average function.
+
+
Syntax
+
postgres=# CREATE [ OR REPLACE ] PROCEDURE procedure_name
+ [ ( {[ argmode ] [ argname ] argtype [ { DEFAULT | := | = } expression ]}[,...]) ]
+ [
+ { IMMUTABLE | STABLE | VOLATILE }
+ | { SHIPPABLE | NOT SHIPPABLE }
+ | {PACKAGE}
+ | [ NOT ] LEAKPROOF
+ | { CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT }
+ | {[ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER | AUTHID DEFINER | AUTHID CURRENT_USER}
+ | COST execution_cost
+ | ROWS result_rows
+ | SET configuration_parameter { [ TO | = ] value | FROM CURRENT }
+ ][ ... ]
+ { IS | AS }
+plsql_body
+/
+
+
Parameter Description
+
+
OR REPLACE
+
Replaces the original definition when two stored procedures are with the same name.
+
+
procedure_name
+
Specifies the name of the stored procedure that is created (optionally with schema names).
+
Value range: a string. It must comply with the naming convention.
+
+
argmode
+
Specifies the mode of an argument.
+
VARIADIC specifies parameters of the array type.
+
+
Value range: IN, OUT, INOUT, and VARIADIC. The default value is IN. Only the parameter of the OUT mode can be followed by VARIADIC. The parameters of OUT and INOUT cannot be used in procedure definition of RETURNS TABLE.
+
+
argname
+
Specifies the argument name.
+
Value range: a string. It must comply with the naming convention.
+
+
argtype
+
Specifies the type of an argument.
+
Value range: a valid data type
+
+
IMMUTABLE, STABLE,
+
...
Specifies a constraint. The function of each parameter is similar to that of CREATE FUNCTION. For details, see CREATE FUNCTION.
+
+
plsql_body
+
Specifies the PL/SQL stored procedure body.
+
When you create a user, or perform other operations requiring password input in a stored procedure, the system catalog and CSV log record the password in plaintext. Therefore, you are advised not to perform such operations in the stored procedure.
+
+
]]>
+
+
+
Function
+
CREATE ROLE is used to create a role.
+
A role is an entity that owns database objects and permissions. In different environments, a role can be considered a user, a group, or both.
+
+
Precautions
+
CREATE ROLE adds a role to a database. The role does not have the LOGIN permission.
Only the user who has the CREATE ROLE permission or a system administrator is allowed to create roles.
+
+
Syntax
+
CREATE ROLE role_name [ [ WITH ] option [ ... ] ] [ ENCRYPTED | UNENCRYPTED ] { PASSWORD | IDENTIFIED BY } { 'password' | DISABLE };
+
The syntax of role information configuration clause option is as follows:
Value range: a string. It must comply with the naming convention rule, and can contain a maximum of 63 characters. If the value contains more than 63 characters, the database truncates it and retains the first 63 characters as the role name. When a role is created, the database will display a message.
+
The identifier must be letters, underscores (_), digits (0-9), or dollar signs ($) and must start with a letter (a-z) or underscore (_).
+
+
+
password
+
Specifies the login password.
+
The new password must:
+
Contain at least eight characters. This is the default length.
Differ from the username or the username spelled backward.
Contain at least three types of the following four types of characters: uppercase characters (A to Z), lowercase characters (a to z), digits (0 to 9), and special characters, including: ~!@#$%^&*()-_=+\|[{}];:,<.>/?
+
Value range: a string
+
+
DISABLE
+
By default, you can change your password unless it is disabled. To disable the password of a user, use this parameter. After the password of a user is disabled, the password will be deleted from the system. The user can connect to the database only through external authentication, for example, Kerberos authentication. Only administrators can enable or disable a password. Common users cannot disable the password of an initial user. To enable a password, run ALTER USER and specify the password.
+
+
ENCRYPTED | UNENCRYPTED
+
Controls whether the password is stored encrypted in the system catalogs. (If neither is specified, the default behavior is determined by the configuration parameter password_encryption.) According to product security requirement, the password must be stored encrypted. Therefore, UNENCRYPTED is forbidden in openGauss. If the password string has already been encrypted in the SHA256 format, it is stored encrypted as it was, regardless of whether ENCRYPTED or UNENCRYPTED is specified (since the system cannot decrypt the specified encrypted password string). This allows reloading of encrypted passwords during dump/restore.
+
+
SYSADMIN | NOSYSADMIN
+
Determines whether a new role is a system administrator. Roles having the SYSADMIN attribute have the highest permission.
+
Value range: If not specified, NOSYSADMIN is the default.
+
+
AUDITADMIN | NOAUDITADMIN
+
Determines whether a role has the audit and management attributes.
+
If not specified, NOAUDITADMIN is the default.
+
+
CREATEDB | NOCREATEDB
+
Determines a role's permission to create databases.
+
A new role does not have the permission to create databases.
+
Value range: If not specified, NOCREATEDB is the default.
+
+
USEFT | NOUSEFT
+
This parameter is reserved and not used in this version.
+
+
CREATEROLE | NOCREATEROLE
+
Determines whether a role will be permitted to create new roles (that is, execute CREATE ROLE and CREATE USER). A role with the CREATEROLE permission can also modify and delete other roles.
+
Value range: If not specified, NOCREATEROLE is the default.
+
+
INHERIT | NOINHERIT
+
Determines whether a role "inherits" the permissions of roles in the same group. You are not advised to set this parameter.
+
+
LOGIN | NOLOGIN
+
Determines whether a role is allowed to log in to a database. A role having the LOGIN attribute can be considered as a user.
+
Value range: If not specified, NOLOGIN is the default.
+
+
REPLICATION | NOREPLICATION
+
Determines whether a role is allowed to initiate streaming replication or put the system in and out of backup mode. A role having the REPLICATION attribute is specific to replication.
+
If not specified, NOREPLICATION is the default.
+
+
INDEPENDENT | NOINDEPENDENT
+
Defines private, independent roles. For a role with the INDEPENDENT attribute, administrators' permissions to control and access this role are separated. The rules are as follows:
+
Administrators have no permission to add, delete, query, modify, copy, or authorize the corresponding table objects without the authorization from the INDEPENDENT role.
System administrators and security administrators with the CREATEROLE attribute have no permission to modify the inheritance relationship of the INDEPENDENT role without the authorization of the INDEPENDENT role.
System administrators have no permission to modify the owner of the table objects for the INDEPENDENT role.
System administrators and security administrators with the CREATEROLE attribute have no permission to remove the INDEPENDENT attribute of the INDEPENDENT role.
System administrators and security administrators with the CREATEROLE attribute have no permission to change the database password of the INDEPENDENT role. The INDEPENDENT role must manage its own password. If the password is lost, it cannot be reset.
The SYSADMIN attribute of a user cannot be changed to the INDEPENDENT attribute.
+
+
CONNECTION LIMIT
+
Specifies how many concurrent connections the role can make.
+
The system administrator is not restricted by this parameter.
The number of concurrent connections of each primary database node is calculated separately (which is the value of connlimit). The number of all connections of openGauss = Value of connlimit x Number of normal primary database nodes.
+
+
Value range: an integer greater than or equal to -1. The default value is -1, which means unlimited.
+
+
VALID BEGIN
+
Sets a date and time when the role's password takes effect. If this clause is omitted, the password takes effect immediately.
+
+
VALID UNTIL
+
Sets a date and time after which the role's password is no longer valid. If this clause is omitted, the password will be valid for all time.
+
+
RESOURCE POOL
+
Sets the name of resource pool used by the role. The name belongs to the system catalog pg_resource_pool.
+
+
PERM SPACE
+
Sets the space available for a user.
+
+
TEMP SPACE
+
Sets the space allocated to the temporary table of a user.
+
+
SPILL SPACE
+
Sets the operator disk flushing space of a user.
+
+
IN ROLE
+
Lists one or more existing roles to which the new role will be immediately added as a new member. You are not advised to set this parameter.
+
+
IN GROUP
+
Specifies an obsolete spelling of IN ROLE. You are not advised to set this parameter.
+
+
ROLE
+
Lists one or more existing roles which are automatically added as members of the new role.
+
+
ADMIN
+
Similar to ROLE. However, ADMIN grants permissions of new roles to other roles.
+
+
USER
+
Specifies an obsolete spelling of the ROLE clause.
+
+
SYSID
+
The SYSID clause is ignored.
+
+
DEFAULT TABLESPACE
+
The DEFAULT TABLESPACE clause is ignored.
+
+
PROFILE
+
The PROFILE clause is ignored.
+
+
PGUSER
+
In the current version, this attribute is reserved only for forward compatibility.
+
]]>
+
+
+
Function
+
CREATE SCHEMA creates a schema.
+
Named objects are accessed either by "qualifying" their names with the schema name as a prefix, or by setting a search path that includes the desired schema. When creating named objects, you can also use the schema name as a prefix.
+
Optionally, CREATE SCHEMA can include sub-commands to create objects within the new schema. The sub-commands are treated essentially the same as separate commands issued after creating the schema. If the AUTHORIZATION clause is used, all the created objects are owned by this user.
+
+
Precautions
+
Only a user with the CREATE permission on the current database can perform this operation.
The owner of an object created by a system administrator in a schema with the same name as a common user is the common user, not the system administrator.
+
+
Examples
+
-- Create a schema named role1 for the role1 role. The owner of the films and winners tables created by the clause is role1.
+postgres=# CREATE SCHEMA AUTHORIZATION role1
+CREATE TABLE films ( title text , release date , awards text[] )
+CREATE VIEW winners AS
+SELECT title , release FROM films WHERE awards IS NOT NULL ;
+
Value range: a string. It must comply with the naming convention rule.
+
+
AUTHORIZATION user_name
+
Specifies the owner of a schema. If schema_name is not specified, user_name will be used as the schema name. In this case, user_name can only be a role name.
+
Value range: an existing username or role name
+
+
schema_element
+
Specifies an SQL statement defining an object to be created within the schema. Currently, only CREATE TABLE, CREATE VIEW, CREATE INDEX, CREATE PARTITION, and GRANT are accepted as clauses within CREATE SCHEMA.
+
Objects created by sub-commands are owned by the user specified by AUTHORIZATION.
+
]]>
+
+
+
Function
+
CREATE SEQUENCE adds a sequence to the current database. The owner of a sequence is the user who creates the sequence.
+
+
Precautions
+
A sequence is a special table that stores arithmetic progressions. It has no actual meaning and is usually used to generate unique identifiers for rows or tables.
If a schema name is given, the sequence is created in the specified schema; otherwise, it is created in the current schema. The sequence name must be different from the names of other sequences, tables, indexes, views in the same schema.
After the sequence is created, functions nextval() and generate_series(1,N) insert data to the table. Make sure that the number of times for invoking nextval is greater than or equal to N+1. Otherwise, errors will be reported because the number of times for invoking function generate_series() is N+1.
CREATE SEQUENCE name [ INCREMENT [ BY ] increment ]
+ [ MINVALUE minvalue | NO MINVALUE | NOMINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE | NOMAXVALUE]
+ [ START [ WITH ] start ] [ CACHE cache ] [ [ NO ] CYCLE | NOCYCLE ]
+ [ OWNED BY { table_name.column_name | NONE } ];
+
+
Parameter Description
+
+
name
+
Specifies the name of a sequence to be created.
+
Value range: a sting containing only lowercase letters, uppercase letters, special characters #_$, and digits
+
+
increment
+
Specifies the step for a sequence. A positive number generates an ascending sequence, and a negative number generates a decreasing sequence.
+
The default value is 1.
+
+
MINVALUE minvalue | NO MINVALUE| NOMINVALUE
+
Specifies the minimum value of the sequence. If MINVALUE is not declared, or NO MINVALUE is declared, the default value of the ascending sequence is 1, and that of the descending sequence is -263-1. NOMINVALUE is equivalent to NO MINVALUE.
+
+
MAXVALUE maxvalue | NO MAXVALUE| NOMAXVALUE
+
Specifies the maximum value of the sequence. If MAXVALUE is not declared, or NO MAXVALUE is declared, the default value of the ascending sequence is 263-1, and that of the descending sequence is -1. NOMAXVALUE is equivalent to NO MAXVALUE.
+
+
start
+
Specifies the start value of the sequence. The default value for an ascending sequence is minvalue and that for a descending sequence is maxvalue.
+
+
cache
+
Specifies the number of sequences stored in the memory for quick access purposes.
+
Default value 1 indicates that one sequence can be generated each time.
+
It is not recommended that you define cache and maxvalue or minvalue at the same time. The continuity of sequences cannot be ensured after cache is defined because unacknowledged sequences may be generated, causing waste of sequences.
+
+
+
CYCLE
+
Recycles sequences after the number of sequences reaches maxvalue or minvalue.
+
If NO CYCLE is specified, any invocation of nextval would return an error after the number of sequences reaches maxvalue or minvalue.
+
NOCYCLE is equivalent to NO CYCLE.
+
The default value is NO CYCLE.
+
If CYCLE is specified, the sequence uniqueness cannot be ensured.
+
+
OWNED BY
+
-
Associates a sequence with a specified column included in a table. In this way, the sequence will be deleted when you delete its associated column or the table where the column belongs to. The associated table and sequence must be owned by the same user and in the same schema. OWNED BY only establishes the association between a table column and the sequence. Sequences on the column do not increase automatically when data is inserted.
+
The default value OWNED BY NONE indicates that such association does not exist.
+
You are not advised to use the sequence created using OWNED BY in other tables. If multiple tables need to share a sequence, the sequence must not belong to a specific table.
+
+
]]>
+
+
+
Function
+
CREATE SYNONYM creates a synonym object. A synonym is an alias of a database object and is used to record the mapping between database object names. You can use synonyms to access associated database objects.
+
+
Precautions
+
The user of a synonym should be its owner.
If the schema name is specified, create a synonym in the specified schema. Otherwise create a synonym in the current schema.
Database objects that can be accessed using synonyms include tables, views, functions, and stored procedures.
To use synonyms, you must have the required permissions on associated objects.
The following DML statements support synonyms: SELECT, INSERT, UPDATE, DELETE, EXPLAIN, and CALL.
The CREATE SYNONYM statement of an associated function or stored procedure cannot be used in a stored procedure. You are advised to use synonyms existing in the pg_synonym system catalog in the stored procedure.
+
+
Syntax
+
CREATE [ OR REPLACE ] SYNONYM synonym_name
+ FOR object_name;
+
+
Parameter Description
+
+
synonym
+
Specifies the name of the synonym to be created, which can contain the schema name.
+
Value range: a string. It must comply with the naming convention.
+
+
object_name
+
Specifies the name of an object that is associated (optionally with schema names).
+
Value range: a string. It must comply with the naming convention.
+
object_name can be the name of an object that does not exist.
+
+
]]>
+
+
+
Function
+
CREATE TABLE is used to create an initially empty table in the current database. The table will be owned by the creator.
It is recommended that the number of column-store tables do not exceed 1000.
The primary key constraint and unique constraint in the table must contain distribution keys.
If an error occurs during table creation, after it is fixed, the system may fail to delete the empty disk files created before the last automatic clearance. This problem seldom occurs and does not affect system running of the database.
Column-store tables support only PARTIAL CLUSTER KEY table-level constraints, but do not support primary and foreign key table-level constraints.
Only the NULL, NOT NULL, and DEFAULT constant values can be used as column-store table constraints.
Whether column-store tables support a delta table is specified by the enable_delta_store parameter. The threshold for storing data into a delta table is specified by the deltarow_threshold parameter.
When JDBC is used, the DEFAULT value can be set through PrepareStatement.
[ WITH ( {storage_parameter = value} [, ... ] ) ]
+[ USING INDEX TABLESPACE tablespace_name ]
+
+
+
Parameter Description
+
+
UNLOGGED
+
If this keyword is specified, the created table is an unlogged table. Data written to unlogged tables is not written to the WALs, which makes them considerably faster than ordinary tables. However, an unlogged table is automatically truncated after a crash or unclean shutdown, incurring data loss risks. Contents of an unlogged table are also not replicated to standby servers. Any indexes created on an unlogged table are not automatically logged as well.
+
Usage scenario: Unlogged tables do not ensure data security. Users can back up data before using unlogged tables; for example, users should back up the data before a system upgrade.
+
Troubleshooting: If data is missing in the indexes of unlogged tables due to some unexpected operations such as an unclean shutdown, users should re-create the indexes with errors.
+
+
GLOBAL | LOCAL
+
When creating a temporary table, you can specify the GLOBAL or LOCAL keyword before TEMP or TEMPORARY. Currently, the two keywords are used to be compatible with the SQL standard. In fact, a local temporary table will be created by openGauss regardless of whether GLOBAL or LOCAL is specified.
+
+
TEMPORARY | TEMP
+
If TEMP or TEMPORARY is specified, the created table is a temporary table. A temporary table is automatically dropped at the end of the current session. Therefore, you can create and use temporary tables in the current session as long as the connected database node in the session is normal. Temporary tables are created only in the current session. If a DDL statement involves operations on temporary tables, a DDL error will be generated. Therefore, you are not advised to perform operations on temporary tables in DDL statements. TEMP is equivalent to TEMPORARY.
+
Temporary tables are visible to the current session through the schema starting with pg_temp start. Users should not delete schema started with pg_temp or pg_toast_temp.
If TEMPORARY or TEMP is not specified when you create a table but its schema is set to that starting with pg_temp_ in the current session, the table will be created as a temporary table.
+
+
+
IF NOT EXISTS
+
Sends a notice, but does not throw an error, if a table with the same name exists.
+
+
table_name
+
Specifies the name of the table to be created.
+
+
column_name
+
Specifies the name of a column to be created in the new table.
+
+
data_type
+
Specifies the data type of the column.
+
+
compress_mode
+
Specifies the compression option of the table, which is only available for row-store tables. The option specifies the algorithm preferentially used by table columns.
+
Value range: DELTA, PREFIX, DICTIONARY, NUMSTR, and NOCOMPRESS
+
+
COLLATE collation
+
Assigns a collation to the column (which must be of a collatable data type). If no collation is specified, the default collation is used.
+
+
LIKE source_table [ like_option ... ]
+
Specifies a table from which the new table automatically copies all column names, their data types, and their not-null constraints.
+
The new table and the original table are decoupled after creation is complete. Changes to the original table will not be applied to the new table, and it is not possible to include data of the new table in scans of the original table.
+
Columns and constraints copied by LIKE are not merged with the same name. If the same name is specified explicitly or in another LIKE clause, an error is reported.
+
The default expressions are copied from the original table to the new table only if INCLUDING DEFAULTS is specified. The default behavior is to exclude default expressions, resulting in the copied columns in the new table having default values null.
The CHECK constraints are copied from the original table to the new table only when INCLUDING CONSTRAINTS is specified. Other types of constraints are never copied to the new table. Not-null constraints are always copied to the new table. These rules also apply to column constraints and table constraints.
Any indexes on the original table will not be created on the new table, unless the INCLUDING INDEXES clause is specified.
STORAGE settings for the copied column definitions are copied only if INCLUDING STORAGE is specified. The default behavior is to exclude STORAGE settings.
If INCLUDING COMMENTS is specified, comments for the copied columns, constraints, and indexes are copied. The default behavior is to exclude comments.
If INCLUDING PARTITION is specified, the partition definitions of the source table are copied to the new table, and the new table no longer uses the PARTITION BY clause. The default behavior is to exclude partition definition of the original table.
If INCLUDING RELOPTIONS is specified, the new table will copy the storage parameter (that is, WITH clause) of the source table. The default behavior is to exclude partition definition of the storage parameter of the original table.
INCLUDING ALL contains the meaning of INCLUDING DEFAULTS, INCLUDING CONSTRAINTS, INCLUDING INDEXES, INCLUDING STORAGE, INCLUDING COMMENTS, INCLUDING PARTITION, and INCLUDING RELOPTIONS.
+
If the source table contains a sequence with the SERIAL, BIGSERIAL, or SMALLSERIRAL data type, or a column in the source table is a sequence by default and the sequence is created for this table by using CREATE SEQUENCE...OWNED BY, these sequences will not be copied to the new table, and another sequence specific to the new table will be created. This is different from earlier versions. To share a sequence between the source table and new table, create a shared sequence (do not use OWNED BY) and set a column in the source table to this sequence.
You are not advised to set a column in the source table to the sequence specific to another table especially when the table is distributed in specific node groups, because doing so may result in CREATE TABLE ... LIKE execution failures. In addition, doing so may cause the sequence to become invalid in the source sequence because the sequence will also be deleted from the source table when it is deleted from the table that the sequence is specific to. To share a sequence among multiple tables, you are advised to create a shared sequence for them.
+
+
+
WITH ( { storage_parameter = value } [, ... ] )
+
Specifies an optional storage parameter for a table or an index.
+
When using Numeric of any precision to define a column, specifies precision p and scale s. When precision and scale are not specified, the input will be displayed.
+
+
The description of parameters is as follows:
+
FILLFACTOR
The fill factor of a table is a percentage from 10 to 100. 100 (complete filling) is the default value. When a smaller fill factor is specified, INSERT operations pack table pages only to the indicated percentage. The remaining space on each page is reserved for updating rows on that page. This gives UPDATE a chance to place the updated copy of a row on the same page, which is more efficient than placing it on a different page. For a table whose entries are never updated, setting the fill factor to 100 (complete filling) is the best choice, but in heavily updated tables a smaller fill factor would be appropriate. The parameter has no meaning for column鈥搒tore tables.
+
Value range: 10鈥?00
+
ORIENTATION
Specifies the storage mode (row-store, column-store, or ORC) of table data. This parameter cannot be modified once it is set.
+
Value range:
+
ROW indicates that table data is stored in rows.
ROW applies to OLTP service and scenarios with a large number of point queries or addition/deletion operations.
+
COLUMN indicates that the data is stored in columns.
COLUMN applies to the data warehouse service, which has a large amount of aggregation computing, and involves a few column operations.
+
+
Default value:
+
If an ordinary tablespace is specified, the default is ROW.
+
COMPRESSION
Specifies the compression level of table data. It determines the compression ratio and time. Generally, the higher the level of compression, the higher the ratio, the longer the time; and the lower the level of compression, the lower the ratio, the shorter the time. The actual compression ratio depends on the distribution mode of table data loaded.
+
Value range:
+
The valid values for column-store tables are YES, NO, LOW, MIDDLE, and HIGH, and the default value is LOW.
+
COMPRESSLEVEL
Specifies the table data compression ratio and duration at the same compression level. This divides a compression level into sublevels, providing more choices for compression ratio and duration. As the value becomes greater, the compression ratio becomes higher and duration longer at the same compression level.
+
Value range: 0 to 3. The default value is 0.
+
MAX_BATCHROW
Specifies the maximum number of rows in a storage unit during data loading. The parameter is only valid for column-store tables.
+
Value range: 10000 to 60000
+
PARTIAL_CLUSTER_ROWS
Specifies the number of records to be partially clustered for storage during data loading. The parameter is only valid for column-store tables.
+
Value range: 600000 to 2147483647
+
DELTAROW_THRESHOLD
Specifies the upper limit of to-be-imported rows for triggering the data import to a delta table when data of a column-store table is to be imported. This parameter takes effect only if enable_delta_store is set to on. The parameter is only valid for column-store tables.
+
Value range: from 0 to 9999. The default value is 100.
+
VERSION
Specifies the version of ORC storage format.
+
Value range: 0.12. ORC 0.12 format is supported currently. More formats will be supported as the development of ORC format.
+
Default value: 0.12
+
+
+
ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP }
+
ON COMMIT determines what to do when you commit a temporary table creation operation. The three options are as follows. Currently, only PRESERVE ROWS and DELETE ROWS can be used.
+
PRESERVE ROWS (default): No special action is taken at the ends of transactions. The temporary table and its table data are unchanged.
DELETE ROWS: All rows in the temporary table will be deleted at the end of each transaction block.
DROP: The temporary table will be dropped at the end of the current transaction block.
+
+
COMPRESS | NOCOMPRESS
+
If you specify COMPRESS in the CREATE TABLE statement, the compression feature is triggered in case of a bulk INSERT operation. If this feature is enabled, a scan is performed for all tuple data within the page to generate a dictionary and then the tuple data is compressed and stored. If NOCOMPRESS is specified, the table is not compressed.
+
Default value: NOCOMPRESS, that is, tuple data is not compressed before storage.
+
+
TABLESPACE tablespace_name
+
Specifies the tablespace where the new table is created. If not specified, the default tablespace is used.
+
+
CONSTRAINT constraint_name
+
Specifies the name of a column or table constraint. The optional constraint clauses specify constraints that new or updated rows must satisfy for an insert or update operation to succeed.
+
There are two ways to define constraints:
+
A column constraint is defined as part of a column definition, and it is bound to a particular column.
A table constraint is not bound to a particular column but can apply to more than one column.
+
+
NOT NULL
+
The column is not allowed to contain null values.
+
+
NULL
+
The column is allowed to contain null values. This is the default setting.
+
This clause is only provided for compatibility with non-standard SQL databases. It is not recommended.
+
+
CHECK ( expression )
+
Specifies an expression producing a Boolean result where the insert or update operation of new or updated rows can succeed only when the expression result is TRUE or UNKNOWN; otherwise, an error is thrown and the database is not altered.
+
A check constraint specified as a column constraint should reference only the column's values, while an expression appearing in a table constraint can reference multiple columns.
+
<>NULL and !=NULL are invalid in an expression. Change them to IS NOT NULL.
+
+
+
DEFAULT default_expr
+
Assigns a default data value for a column. The value can be any variable-free expressions. (Subqueries and cross-references to other columns in the current table are not allowed.) The data type of the default expression must match the data type of the column.
+
The default expression will be used in any insert operation that does not specify a value for the column. If there is no default value for a column, then the default value is null.
+
+
UNIQUE index_parameters
+
UNIQUE ( column_name [, ... ] ) index_parameters
+
Specifies that a group of one or more columns of a table can contain only unique values.
+
For the purpose of a unique constraint, null is not considered equal.
Specifies that a column or columns of a table can contain only unique (non-duplicate) and non-null values.
+
Only one primary key can be specified for a table.
+
+
DEFERRABLE | NOT DEFERRABLE
+
They determine whether the constraint is deferrable. A constraint that is not deferrable will be checked immediately after every command. Checking of constraints that are deferrable can be postponed until the end of the transaction using the SET CONSTRAINTS command. NOT DEFERRABLE is the default value. Currently, only UNIQUE and PRIMARY KEY constraints accept this clause. All the other constraints are not deferrable.
+
+
PARTIAL CLUSTER KEY
+
Specifies a partial cluster key for storage. When importing data to a column-store table, you can perform local data sorting by specified columns (single or multiple).
+
+
INITIALLY IMMEDIATE | INITIALLY DEFERRED
+
If a constraint is deferrable, this clause specifies the default time to check the constraint.
+
If the constraint is INITIALLY IMMEDIATE (default value), it is checked after each statement.
If the constraint is INITIALLY DEFERRED, it is checked only at the end of the transaction.
+
The constraint check time can be altered using the SET CONSTRAINTS statement.
+
+
USING INDEX TABLESPACE tablespace_name
+
Allows selection of the tablespace in which the index associated with a UNIQUE or PRIMARY KEY constraint will be created. If not specified, default_tablespace is consulted, or the default tablespace in the database if default_tablespace is empty.
+
]]>
+
+
+
Function
+
CREATE TABLE AS creates a table from the results of a query.
+
It creates a table and fills it with data obtained using SELECT. The table columns have the names and data types associated with the output columns of SELECT (except that you can override the SELECT output column names by giving an explicit list of new column names).
+
CREATE TABLE AS queries a source table once and writes the data in a new table. The result in the query view changes with the source table. In contrast, the view re-computes and defines its SELECT statement at each query.
+
+
Precautions
+
This statement cannot be used to create a partitioned table.
If an error occurs during table creation, after it is fixed, the system may fail to delete the disk files that are created before the last automatic clearance and whose size is not 0. This problem seldom occurs and does not affect system running of the database.
+
+
Syntax
+
CREATE [ UNLOGGED ] TABLE table_name
+ [ (column_name [, ...] ) ]
+ [ WITH ( {storage_parameter = value} [, ... ] ) ]
+ [ COMPRESS | NOCOMPRESS ]
+ [ TABLESPACE tablespace_name ]
+ AS query
+ [ WITH [ NO ] DATA ];
+
+
Parameter Description
+
+
UNLOGGED
+
Specifies that the table is created as an unlogged table. Data written to unlogged tables is not written to the WALs, which makes them considerably faster than ordinary tables. However, they are not crash-safe: an unlogged table is automatically truncated after a crash or unclean shutdown. The contents of an unlogged table are also not replicated to standby servers. Any indexes created on an unlogged table are automatically unlogged as well.
+
Usage scenario: Unlogged tables do not ensure data security. Users can back up data before using unlogged tables; for example, users should back up the data before a system upgrade.
Troubleshooting: If data is missing in the indexes of unlogged tables due to some unexpected operations such as an unclean shutdown, users should re-create the indexes with errors.
+
+
table_name
+
Specifies the name of the table to be created.
+
Value range: a string. It must comply with the naming convention.
+
+
column_name
+
Specifies the name of a column to be created in the new table.
+
Value range: a string. It must comply with the naming convention.
+
+
WITH ( storage_parameter [= value] [, ... ] )
+
Specifies an optional storage parameter for a table or an index. See details of parameters below.
+
FILLFACTOR
The fill factor of a table is a percentage from 10 to 100. 100 (complete filling) is the default value. When a smaller fill factor is specified, INSERT operations pack table pages only to the indicated percentage. The remaining space on each page is reserved for updating rows on that page. This gives UPDATE a chance to place the updated copy of a row on the same page, which is more efficient than placing it on a different page. For a table whose entries are never updated, setting the fill factor to 100 (complete filling) is the best choice, but in heavily updated tables a smaller fill factor would be appropriate. The parameter is only valid for row鈥搒tore tables.
+
Value range: 10鈥?00
+
ORIENTATION
Value range:
+
COLUMN: The data will be stored in columns.
+
ROW (default value): The data will be stored in rows.
+
COMPRESSION
Specifies the compression level of table data. It determines the compression ratio and time. Generally, the higher the level of compression, the higher the ratio, the longer the time; and the lower the level of compression, the lower the ratio, the shorter the time. The actual compression ratio depends on the distribution mode of table data loaded.
+
Value range:
+
The valid values for column-store tables are YES, NO, LOW, MIDDLE, and HIGH, and the default value is LOW.
+
Valid values for row-store tables are YES and NO, and the default value is NO.
+
MAX_BATCHROW
Specifies the maximum number of rows in a storage unit during data loading. The parameter is only valid for column-store tables.
+
Value range: 10000 to 60000
+
+
+
COMPRESS / NOCOMPRESS
+
Specifies keyword COMPRESS during the creation of a table, so that the compression feature is triggered in case of bulk INSERT operations. If this feature is enabled, a scan is performed for all tuple data within the page to generate a dictionary and then the tuple data is compressed and stored. If NOCOMPRESS is specified, the table is not compressed.
+
Default value: NOCOMPRESS, that is, tuple data is not compressed before storage.
+
+
TABLESPACE tablespace_name
+
Specifies that the new table will be created in the tablespace_name tablespace. If not specified, the default tablespace is used.
+
+
AS query
+
Specifies a SELECT or VALUES command, or an EXECUTE command that runs a prepared SELECT or VALUES query.
+
+
[ WITH [ NO ] DATA ]
+
Specifies whether the data produced by the query should be copied to the new table. By default, the data will be copied. If the value NO is used, only the table structure will be copied.
+
]]>
+
+
+
Function
+
CREATE TABLE PARTITION creates a partitioned table. A partitioned table is a logical table that is divided into several physical partitions for storage based on a specific plan. Data is stored in physical partitions not the logical table.
+
The common forms of partitioning include range partitioning, hash partitioning, list partitioning, and value partitioning. Currently, the system supports only range partitioning for row-store and column-store tables.
+
In range partitioning, a table is partitioned based on ranges defined by values in one or more columns, with no overlap between the ranges of values assigned to different partitions. Each range has a dedicated partition for data storage.
+
The range partitioning policy refers to how data is inserted into partitions. Currently, range partitioning only allows the use of the range partitioning policy.
+
In range partitioning, a table is partitioned based on partition key values. If a record can be mapped to a partition, it is inserted into the partition; if it cannot, an error message is returned. Range partitioning is the most commonly used partitioning policy.
+
Partitioning can provide several benefits:
+
Query performance can be improved drastically in certain situations, particularly when most of the heavily accessed rows of the table are in a single partition or a small number of partitions. Partitioning narrows the range of data search and improves data access efficiency.
In the case of an insert or update operation on most portions of a single partition, performance can be improved by taking advantage of continuous scan of that partition instead of partitions scattered across the whole table.
Frequent loading or deletion operations on records in a separate partition can be accomplished by reading or removing that partition. It also entirely avoids the VACUUM overload caused by bulk DELETE operations (only for range partitioning).
+
+
Precautions
+
A partitioned table supports unique and primary key constraints. The constraint keys of these constraints must contain all partition keys.
+
+
Examples
+
-- Create a range-partitioned table tpcds.web_returns_p1.
+postgres=# CREATE TABLE tpcds.web_returns_p1
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER ,
+WR_REFUNDED_CDEMO_SK INTEGER ,
+WR_REFUNDED_HDEMO_SK INTEGER ,
+WR_REFUNDED_ADDR_SK INTEGER ,
+WR_RETURNING_CUSTOMER_SK INTEGER ,
+WR_RETURNING_CDEMO_SK INTEGER ,
+WR_RETURNING_HDEMO_SK INTEGER ,
+WR_RETURNING_ADDR_SK INTEGER ,
+WR_WEB_PAGE_SK INTEGER ,
+WR_REASON_SK INTEGER ,
+WR_ORDER_NUMBER BIGINT NOT NULL ,
+WR_RETURN_QUANTITY INTEGER ,
+WR_RETURN_AMT DECIMAL ( 7 , 2 ) ,
+WR_RETURN_TAX DECIMAL ( 7 , 2 ) ,
+WR_RETURN_AMT_INC_TAX DECIMAL ( 7 , 2 ) ,
+WR_FEE DECIMAL ( 7 , 2 ) ,
+WR_RETURN_SHIP_COST DECIMAL ( 7 , 2 ) ,
+WR_REFUNDED_CASH DECIMAL ( 7 , 2 ) ,
+WR_REVERSED_CHARGE DECIMAL ( 7 , 2 ) ,
+WR_ACCOUNT_CREDIT DECIMAL ( 7 , 2 ) ,
+WR_NET_LOSS DECIMAL ( 7 , 2 )
+ )
+WITH ( ORIENTATION = COLUMN , COMPRESSION=MIDDLE )
+PARTITION BY RANGE ( WR_RETURNED_DATE_SK )
+ (
+PARTITION P1 VALUES LESS THAN ( 2450815 ) ,
+PARTITION P2 VALUES LESS THAN ( 2451179 ) ,
+PARTITION P3 VALUES LESS THAN ( 2451544 ) ,
+PARTITION P4 VALUES LESS THAN ( 2451910 ) ,
+PARTITION P5 VALUES LESS THAN ( 2452275 ) ,
+PARTITION P6 VALUES LESS THAN ( 2452640 ) ,
+PARTITION P7 VALUES LESS THAN ( 2453005 ) ,
+PARTITION P8 VALUES LESS THAN ( MAXVALUE )
+ ) ;
+
+-- Query the number of rows in the P1 partition.
+postgres=# SELECT COUNT ( * ) FROM tpcds.web_returns_p1 PARTITION FOR ( 2450815 ) ;
+count
+--------
+0
+ ( 1 row )
+Example 2: Create a range-partitioned table tpcds.web_returns_p2. The table has eight partitions and their partition keys are of the integer type. The upper limit of the eighth partition is MAXVALUE.The ranges of the partitions are: wr_returned_date_sk < 2450815 , 2450815 鈮?wr_returned_date_sk < 2451179 , 2451179 鈮?wr_returned_date_sk < 2451544 , 2451544 鈮?wr_returned_date_sk < 2451910 , 2451910 鈮?wr_returned_date_sk < 2452275 , 2452275 鈮?wr_returned_date_sk < 2452640 , 2452640 鈮?wr_returned_date_sk < 2453005 , and wr_returned_date_sk 鈮?2453005.
+The tablespace of the tpcds.web_returns_p2 partitioned table is example1. Partitions P1 to P7 have no specified tablespaces , and use the example1 tablespace of the tpcds.web_returns_p2 partitioned table. The tablespace of the P8 partitioned table is example2.
+Assume that the following data directories of the database nodes are empty directories for which user dwsadmin has the read and write permissions: /pg_location/mount1/path1 , /pg_location/mount2/path2 , /pg_location/mount3/path3 , and /pg_location/mount4/path4.
+postgres=# CREATE TABLESPACE example1 RELATIVE LOCATION ' tablespace1/tablespace_1 ' ;
+postgres=# CREATE TABLESPACE example2 RELATIVE LOCATION ' tablespace2/tablespace_2 ' ;
+postgres=# CREATE TABLESPACE example3 RELATIVE LOCATION ' tablespace3/tablespace_3 ' ;
+postgres=# CREATE TABLESPACE example4 RELATIVE LOCATION ' tablespace4/tablespace_4 ' ;
+postgres=# CREATE TABLE tpcds.web_returns_p2
+ (
+WR_RETURNED_DATE_SK INTEGER ,
+WR_RETURNED_TIME_SK INTEGER ,
+WR_ITEM_SK INTEGER NOT NULL ,
+WR_REFUNDED_CUSTOMER_SK INTEGER ,
+WR_REFUNDED_CDEMO_SK INTEGER ,
+WR_REFUNDED_HDEMO_SK INTEGER ,
+WR_REFUNDED_ADDR_SK INTEGER ,
+WR_RETURNING_CUSTOMER_SK INTEGER ,
+WR_RETURNING_CDEMO_SK INTEGER ,
+WR_RETURNING_HDEMO_SK INTEGER ,
+WR_RETURNING_ADDR_SK INTEGER ,
+WR_WEB_PAGE_SK INTEGER ,
+WR_REASON_SK INTEGER ,
+WR_ORDER_NUMBER BIGINT NOT NULL ,
+WR_RETURN_QUANTITY INTEGER ,
+WR_RETURN_AMT DECIMAL ( 7 , 2 ) ,
+WR_RETURN_TAX DECIMAL ( 7 , 2 ) ,
+WR_RETURN_AMT_INC_TAX DECIMAL ( 7 , 2 ) ,
+WR_FEE DECIMAL ( 7 , 2 ) ,
+WR_RETURN_SHIP_COST DECIMAL ( 7 , 2 ) ,
+WR_REFUNDED_CASH DECIMAL ( 7 , 2 ) ,
+WR_REVERSED_CHARGE DECIMAL ( 7 , 2 ) ,
+WR_ACCOUNT_CREDIT DECIMAL ( 7 , 2 ) ,
+WR_NET_LOSS DECIMAL ( 7 , 2 )
+ )
+TABLESPACE example1
+PARTITION BY RANGE ( WR_RETURNED_DATE_SK )
+ (
+PARTITION P1 VALUES LESS THAN ( 2450815 ) ,
+PARTITION P2 VALUES LESS THAN ( 2451179 ) ,
+PARTITION P3 VALUES LESS THAN ( 2451544 ) ,
+PARTITION P4 VALUES LESS THAN ( 2451910 ) ,
+PARTITION P5 VALUES LESS THAN ( 2452275 ) ,
+PARTITION P6 VALUES LESS THAN ( 2452640 ) ,
+PARTITION P7 VALUES LESS THAN ( 2453005 ) ,
+PARTITION P8 VALUES LESS THAN ( MAXVALUE ) TABLESPACE example2
+ )
+ENABLE ROW MOVEMENT ;
+
+-- Create a partitioned table using LIKE.
+postgres=# CREATE TABLE tpcds.web_returns_p3 ( LIKE tpcds.web_returns_p2 INCLUDING PARTITION ) ;
+
{ INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES | STORAGE | COMMENTS | RELOPTIONS| ALL }
+
+
index_parameters is as follows:
[ WITH ( {storage_parameter = value} [, ... ] ) ]
+[ USING INDEX TABLESPACE tablespace_name ]
+
+
+
Parameter Description
+
+
IF NOT EXISTS
+
Sends a notice, but does not throw an error, if a table with the same name exists.
+
+
partition_table_name
+
Specifies the name of the partitioned table.
+
Value range: a string. It must comply with the naming convention.
+
+
column_name
+
Specifies the name of a column to be created in the new table.
+
Value range: a string. It must comply with the naming convention.
+
+
data_type
+
Specifies the data type of the column.
+
+
COLLATE collation
+
Assigns a collation to the column (which must be of a collatable data type). If no collation is specified, the default collation is used.
+
+
CONSTRAINT constraint_name
+
Specifies the name of a column or table constraint. The optional constraint clauses specify constraints that new or updated rows must satisfy for an insert or update operation to succeed.
+
There are two ways to define constraints:
+
A column constraint is defined as part of a column definition, and it is bound to a particular column.
A table constraint is not bound to a particular column but can apply to more than one column.
+
+
LIKE source_table [ like_option ... ]
+
Specifies a table from which the new table automatically copies all column names, their data types, and their not-null constraints.
+
Unlike INHERITS, the new table and original table are decoupled after creation is complete. Changes to the original table will not be applied to the new table, and it is not possible to include data of the new table in scans of the original table.
+
Default expressions for the copied column definitions will be copied only if INCLUDING DEFAULTS is specified. The default behavior is to exclude default expressions, resulting in the copied columns in the new table having default values null.
+
Not-null constraints are always copied to the new table. CHECK constraints will only be copied if INCLUDING CONSTRAINTS is specified; other types of constraints will never be copied. These rules also apply to column constraints and table constraints.
+
Unlike those of INHERITS, columns and constraints copied by LIKE are not merged with similarly named columns and constraints. If the same name is specified explicitly or in another LIKE clause, an error is reported.
+
Any indexes on the original table will not be created on the new table, unless the INCLUDING INDEXES clause is specified.
STORAGE settings for the copied column definitions are copied only if INCLUDING STORAGE is specified. The default behavior is to exclude STORAGE settings.
If INCLUDING COMMENTS is specified, comments for the copied columns, constraints, and indexes are copied. The default behavior is to exclude comments.
If INCLUDING RELOPTIONS is specified, the new table will copy the storage parameter (that is, WITH clause) of the source table. The default behavior is to exclude partition definition of the storage parameter of the source table.
INCLUDING ALL contains the meaning of INCLUDING DEFAULTS, INCLUDING CONSTRAINTS, INCLUDING INDEXES, INCLUDING STORAGE, INCLUDING COMMENTS, INCLUDING PARTITION, and INCLUDING RELOPTIONS.
+
+
WITH ( storage_parameter [= value] [, ... ] )
+
Specifies an optional storage parameter for a table or an index. Optional parameters are as follows:
+
FILLFACTOR
The fill factor of a table is a percentage from 10 to 100. 100 (complete filling) is the default value. When a smaller fill factor is specified, INSERT operations pack table pages only to the indicated percentage. The remaining space on each page is reserved for updating rows on that page. This gives UPDATE a chance to place the updated copy of a row on the same page, which is more efficient than placing it on a different page. For a table whose entries are never updated, setting the fill factor to 100 (complete filling) is the best choice, but in heavily updated tables a smaller fill factor would be appropriate. The parameter has no meaning for column鈥搒tore tables.
+
Value range: 10鈥?00
+
ORIENTATION
Determines the storage mode of the data in the table.
+
Value range:
+
COLUMN: The data will be stored in columns.
ROW (default value): The data will be stored in rows.
orientation cannot be modified.
+
+
+
COMPRESSION
Valid values for column-store tables are LOW, MIDDLE, HIGH, YES, and NO, and the compression level increases accordingly. The default is LOW.
Valid values for row-store tables are YES and NO, and the default value is NO.
+
MAX_BATCHROW
Specifies the maximum number of rows in a storage unit during data loading. The parameter is only valid for column-store tables.
+
Value range: 10000 to 60000
+
PARTIAL_CLUSTER_ROWS
Specifies the number of records to be partially clustered for storage during data loading. The parameter is only valid for column-store tables.
+
Value range: a number greater than or equal to 100000 The value is a multiple of MAX_BATCHROW.
+
DELTAROW_THRESHOLD
A reserved parameter. The parameter is only valid for column-store tables.
+
Value range: 0 to 9999
+
+
+
COMPRESS / NOCOMPRESS
+
Specifies keyword COMPRESS during the creation of a table, so that the compression feature is triggered in case of bulk INSERT operations. If this feature is enabled, a scan is performed for all tuple data within the page to generate a dictionary and then the tuple data is compressed and stored. If NOCOMPRESS is specified, the table is not compressed.
+
Default value: NOCOMPRESS, that is, tuple data is not compressed before storage.
+
+
TABLESPACE tablespace_name
+
Specifies that the new table will be created in the tablespace_name tablespace. If not specified, the default tablespace is used.
+
+
+
me="en-us_topic_0237122119_en-us_topic_0059777586_l00efc30fe63048ffa2ef68c5b18bb455">PARTITION BY RANGE(partition_key)
Creates a range partition. partition_key is the name of the partition key.
+
(1) Assume that the VALUES LESS THAN syntax is used.
+
In this case, a maximum of four partition keys are supported.
+
+
Data types supported by the partition keys are as follows: SMALLINT, INTEGER, BIGINT, DECIMAL, NUMERIC, REAL, DOUBLE PRECISION, CHARACTER VARYING(n), VARCHAR(n), CHARACTER(n), CHAR(n), CHARACTER, CHAR, TEXT, NVARCHAR2, NAME, TIMESTAMP[(p)] [WITHOUT TIME ZONE], TIMESTAMP[(p)] [WITH TIME ZONE], and DATE.
+
(2) Assume that the START END syntax is used.
+
In this case, only one partition key is supported.
+
+
Data types supported by the partition key are as follows: SMALLINT, INTEGER, BIGINT, DECIMAL, NUMERIC, REAL, DOUBLE PRECISION, TIMESTAMP[(p)] [WITHOUT TIME ZONE], TIMESTAMP[(p)] [WITH TIME ZONE], and DATE.
+
+
PARTITION partition_name VALUES LESS THAN ( { partition_value | MAXVALUE } )
+
Specifies the information of partitions. partition_name is the name of a range partition. partition_value is the upper limit of a range partition, and the value depends on the type of partition_key. MAXVALUE usually specifies the upper limit of the last range partition.
+
Each partition requires an upper limit.
The data type of the upper limit must be the same as that of the partition key.
In a partition list, partitions are arranged in ascending order of upper limits. A partition with a smaller upper limit value is placed before another partition with a larger one.
+
+
+
+
me="en-us_topic_0237122119_li2094151861116">PARTITION partition_name {START (partition_value) END (partition_value) EVERY (interval_value)} | {START (partition_value) END (partition_value|MAXVALUE)} | {START(partition_value)} | {END (partition_value | MAXVALUE)}
Specifies the information of partitions.
+
partition_name: name or name prefix of a range partition. It is the name prefix only in the following cases (assuming that partition_name is p1):
If START+END+EVERY is used, the names of partitions will be defined as p1_1, p1_2, and the like. For example, if PARTITION p1 START(1) END(4) EVERY(1) is defined, the generated partitions are [1, 2), [2, 3), and [3, 4), and their names are p1_1, p1_2, and p1_3. In this case, p1 is a name prefix.
If the defined statement is in the first place and has START specified, the range (MINVALUE, START) will be automatically used as the first actual partition, and its name will be p1_0. The other partitions are then named p1_1, p1_2, and the like. For example, if PARTITION p1 START(1), PARTITION p2 START(2) is defined, generated partitions are (MINVALUE, 1), [1, 2), and [2, MAXVALUE), and their names will be p1_0, p1_1, and p2. In this case, p1 is a name prefix and p2 is a partition name. MINVALUE means the minimum value.
+
partition_value: start value or end value of a range partition. The value depends on partition_key and cannot be MAXVALUE.
interval_value: width of each partition for dividing the [START, END) range. It cannot be MAXVALUE. If the value of (END 鈥?START) divided by EVERY has a remainder, the width of only the last partition is less than the value of EVERY.
MAXVALUE: upper limit of the last range partition.
+
If the defined statement is in the first place and has START specified, the range (MINVALUE, START) will be automatically used as the first actual partition.
The START END syntax must comply with the following rules:
The value of START (if any, same for the following situations) in each partition_start_end_item must be smaller than that of END.
In two adjacent partition_start_end_item statements, the value of the first END must be equal to that of the second START.
The value of EVERY in each partition_start_end_item must be a positive number (in ascending order) and must be smaller than END minus START.
Each partition includes the start value (unless it is MINVALUE) and excludes the end value. The format is as follows: [START, END).
Partitions created by the same partition_start_end_item belong to the same tablespace.
If partition_name is a name prefix of a partition, the length must not exceed 57 bytes. If there are more than 57 bytes, the prefix will be automatically truncated.
When creating or modifying a partitioned table, ensure that the total number of partitions in the table does not exceed the maximum value (32767).
+
In statements for creating partitioned tables, START END and LESS THAN cannot be used together.
The START END syntax in a partitioned table creation SQL statement will be replaced by the VALUES LESS THAN syntax when gs_dump is executed.
+
+
+
{ ENABLE | DISABLE } ROW MOVEMENT
+
Sets row movement.
+
If the tuple value is updated on the partition key during the UPDATE action, the partition where the tuple is located is altered. Setting this parameter enables error messages to be reported or movement of the tuple between partitions.
+
Value range:
+
ENABLE (default value): Row movement is enabled.
DISABLE: Row movement is disabled.
+
]]>
+
+
+
Function
+
CREATE TABLESPACE creates a tablespace in a database.
+
+
Precautions
+
Only system administrators can create a tablespace.
Do not run CREATE TABLESPACE in a transaction block.
If executing CREATE TABLESPACE fails but the internal directory (or file) has been created, the directory (or file) will remain. You need to manually clear it before creating the tablespace again. If there are residual files of soft links for the tablespace in the data directory, delete the residual files, and then perform O&M operations.
CREATE TABLESPACE cannot be used for two-phase transactions. If it fails on some nodes, the execution cannot be rolled back.
For details about how to prepare for creating tablespaces, see the description of parameters below.
+
+
Examples
+
-- Create a tablespace.
+postgres=# CREATE TABLESPACE ds_location1 RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+
+-- Create a tablespace and set its owner to user joe.
+postgres=# CREATE TABLESPACE ds_location2 OWNER joe RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+
The with_option_clause syntax for creating a general tablespace is as follows:
+
WITH ( {filesystem= { 'general'| "general" | general} |
+ random_page_cost = { 'value ' | value } |
+ seq_page_cost = { 'value ' | value }}[,...])
+
+
Parameter Description
+
+
tablespace_name
+
Specifies name of a tablespace to be created.
+
The tablespace name must be distinct from the name of any existing tablespace in openGauss and cannot start with "pg", which are reserved for system catalog spaces.
+
Value range: a string. It must comply with the naming convention.
+
+
OWNER user_name
+
Specifies the name of the user who will own the tablespace. If omitted, the default owner is the current user.
+
Only system administrators can create tablespaces, but they can use the OWNER clause to assign ownership of tablespaces to non-Sysadmin administrators.
+
Value range: a string. It must be an existing user.
+
+
RELATIVE
+
Relative path. The LOCATION directory is relative to the data directory in each database node.
+
Directory hierarchy: the relative path of the database node directory /pg_location/
+
A relative path contains a maximum of two levels.
+
+
LOCATION directory
+
Specifies the directory used for the tablespace. The directory must meet the following requirements:
+
The openGauss system user must have the read and write permissions on the directory, and the directory must be empty. If the directory does not exist, the system automatically creates it.
The directory must be an absolute path, and does not contain special characters, such as dollar sign ($) and greater-than sign (>).
The directory cannot be specified under the database data directory.
The directory must be a local path.
+
Value range: a string. It must be a valid directory.
+
+
MAXSIZE 'space_size'
+
Specifies the maximum value of the tablespace in a single database node.
+
Value range: a string consisting of a positive integer and unit. The unit can be KB, MB, GB, TB, or PB currently. The unit of parsed value is KB and cannot exceed the range that can be expressed in 64 bits, which is 1 KB to 9007199254740991 KB.
+
+
random_page_cost
+
Specifies the cost of randomly reading the page overhead.
+
Value range: 0 to 1.79769e+308
+
Default value: value of the GUC parameter random_page_cost
+
+
seq_page_cost
+
Specifies the cost of reading the page overhead in specified order.
+
Value range: 0 to 1.79769e+308
+
Default value: value of GUC parameter seq_page_cost
+
]]>
+
+
+
Function
+
CREATE TEXT SEARCH CONFIGURATION creates a text search configuration. A text search configuration specifies a text search parser that can divide a string into tokens, plus dictionaries that can be used to determine which tokens are of interest for searching.
+
+
Precautions
+
If only the parser is specified, the new text search configuration initially has no mapping from token types to dictionaries, and therefore will ignore all words. Subsequently, ALTER TEXT SEARCH CONFIGURATION must be used to create mapping to make the configuration useful. If COPY is specified, the parser, mapping and parameters of the text search configuration is copied automatically.
If the schema name is given, the text search configuration will be created in the specified schema. Otherwise, the configuration will be created in the current schema.
The user who defines a text search configuration becomes its owner.
PARSER and COPY options are mutually exclusive, because when an existing configuration is copied, its parser selection is copied too.
If only the parser is specified, the new text search configuration initially has no mapping from token types to dictionaries, and therefore will ignore all words.
+
+
Examples
+
-- Create a text search configuration.
+postgres=# CREATE TEXT SEARCH CONFIGURATION ngram2 ( parser=ngram ) WITH ( gram_size = 2 , grapsymbol_ignore = false ) ;
+
+-- Create a text search configuration.
+postgres=# CREATE TEXT SEARCH CONFIGURATION ngram3 ( copy=ngram2 ) WITH ( gram_size = 2 , grapsymbol_ignore = false ) ;
+
+
Syntax
+
CREATE TEXT SEARCH CONFIGURATION name
+ ( PARSER = parser_name | COPY = source_config )
+ [ WITH ( {configuration_option = value} [, ...] )];
+
+
Parameter Description
+
+
name
+
Specifies the name of the text search configuration to be created. The name can be schema-qualified.
+
+
parser_name
+
Specifies the name of the text search parser to use for this configuration.
+
+
source_config
+
Specifies the name of an existing text search configuration to copy.
+
+
configuration_option
+
Specifies parameters for the text search configuration, particularly for the parser executed by parser_name or contained by source_config.
+
Value range: The default and ngram parsers are supported. The parser of default type has no corresponding configuration_option. Table 1 lists configuration_option for ngram parsers.
+
Table 1 Configuration parameters for ngram parsers
Parser
+
+
Parameter
+
+
Description
+
+
Value Range
+
+
+
+
ngram
+
+
gram_size
+
+
Length of word segmentation
+
+
Integer, 1 to 4
+
Default value: 2
+
+
+
punctuation_ignore
+
+
Whether to ignore punctuations
+
+
true (default value): Ignore punctuations.
false: Do not ignore punctuations.
+
+
+
grapsymbol_ignore
+
+
Whether to ignore graphical characters
+
+
true: Ignore graphical characters.
false (default value): Do not ignore graphical characters.
+
+
+
+
+
+
+
]]>
+
+
+
Function
+
CREATE TEXT SEARCH DICTIONARY creates a full-text retrieval dictionary. A dictionary is used to identify and process particular words during full-text retrieval.
+
Dictionaries are created by using predefined templates (defined in the PG_TS_TEMPLATE system catalog). Five types of dictionaries can be created, Simple, Ispell, Synonym, Thesaurus, and Snowball. These dictionaries are used to handle different types of tasks.
+
+
Precautions
+
A user with the SYSADMIN permission can create a dictionary. Then, the user automatically becomes the owner of the dictionary.
A dictionary cannot be created in pg_temp mode.
After a dictionary is created or modified, any modification to the customized dictionary definition file will not affect the dictionary in the database. To make such modifications take effect in the dictionary in the database, run the ALTER statement to update the definition file of the dictionary.
+
+
Syntax
+
CREATE TEXT SEARCH DICTIONARY name (
+ TEMPLATE = template
+ [, option = value [, ... ]]
+);
+
+
Parameter Description
+
+
name
+
Specifies the name of a dictionary to be created. (If you do not specify a schema name, the dictionary will be created in the current schema.)
+
Value range: a string, which complies with the identifier naming convention. A value can contain a maximum of 63 characters.
+
+
template
+
Specifies a template name.
+
Value range: templates (Simple, Synonym, Thesaurus, Ispell, and Snowball) defined in the PG_TS_TEMPLATE system catalog
Specifies a parameter name. Each type of dictionaries has a template containing their custom parameters. Parameters function in a way irrelevant to their setting sequence.
+
Parameters for a Simple dictionary
STOPWORDS
Specifies the name of a file listing stop words. The default file name extension is .stop. In the file, each line defines a stop word. Dictionaries will ignore blank lines and spaces in the file and convert stop-word phrases into lowercase.
+
ACCEPT
Specifies whether to accept a non-stop word as recognized. Default value: true
+
If ACCEPT=true is set for a Simple dictionary, no token will be passed to subsequent dictionaries. In this case, you are advised to place the Simple dictionary at the end of the dictionary list. If ACCEPT=false is set, you are advised to place the Simple dictionary before at least one dictionary in the list.
+
FILEPATH
Specifies the directory for storing dictionary files. The directory can be a local directory or an OBS directory. The local directory format is file://absolute_path. The OBS directory format is obs://bucket_name/path accesskey=ak secretkey=sk region=rg. The default value is the directory where predefined dictionary files are located. If any of the FILEPATH and STOPWORDS parameters is specified, the other one must also be specified.
+
+
Parameters for a Synonym dictionary
SYNONYM
Specifies the name of the definition file for a Synonym dictionary. The default file name extension is .syn.
+
The file is a list of synonyms. Each line is in the format of token synonym, that is, token and its synonym separated by a space.
+
CASESENSITIVE
Specifies whether tokens and their synonyms are case sensitive. The default value is false, indicating that tokens and synonyms in dictionary files will be converted into lowercase. If this parameter is set to true, they will not be converted into lowercase.
+
FILEPATH
Specifies the directory for storing Synonym dictionary files. The directory can be a local directory or an OBS directory. The local directory format is file://absolute_path. The OBS directory format is obs://bucket_name/path accesskey=ak secretkey=sk region=rg. The default value is the directory where predefined dictionary files are located.
+
+
Parameters for a Thesaurus dictionary
DICTFILE
Specifies the name of a dictionary definition file. The default file name extension is .ths.
+
The file is a list of synonyms. Each line is in the format of sample words:indexed words. The colon (:) is used as a separator between a phrase and its substitute word. If multiple sample words are matched, the TZ selects the longest one.
+
+
DICTIONARY
Specifies the name of a subdictionary used for word normalization. This parameter is mandatory and only one subdictionary name can be specified. The specified subdictionary must exist. It is used to identify and normalize input text before phrase matching.
+
If an input word cannot be recognized by the subdictionary, an error will be reported. In this case, remove the word or update the subdictionary to make the word recognizable. In addition, an asterisk (*) can be placed at the beginning of an indexed word to skip the application of a subdictionary on it, but all sample words must be recognizable by the subdictionary.
+
If the sample words defined in the dictionary file contain stop words defined in the subdictionary, use question marks (?) to replace them. Assume that a and the are stop words defined in the subdictionary.
? one ? two : swsw
+
+
a one the two and the one a two will be matched and output as swsw.
+
FILEPATH
Specifies the directory for storing dictionary definition files. The directory can be a local directory or an OBS directory. The local directory format is file://absolute_path. The OBS directory format is obs://bucket_name/path accesskey=ak secretkey=sk region=rg. The default value is the directory where predefined dictionary files are located.
+
+
Parameters for an Ispell dictionary
DICTFILE
Specifies the name of a dictionary definition file. The default file name extension is .dict.
+
AFFFILE
Specifies the name of an affix file. The default file name extension is .affix.
+
STOPWORDS
Specifies the name of a file listing stop words. The default file name extension is .stop. The file content format is the same as that of the file for a Simple dictionary.
+
FILEPATH
Specifies the directory for storing dictionary files. The directory can be a local directory or an OBS directory. The local directory format is file://absolute_path. The OBS directory format is obs://bucket_name/path accesskey=ak secretkey=sk region=rg. The default value is the directory where predefined dictionary files are located.
+
+
Parameters for a Snowball dictionary
LANGUAGE
Specifies the name of a language whose stemming algorithm will be used. According to spelling rules in the language, the algorithm normalizes the variants of an input word into a basic word or a stem.
+
STOPWORDS
Specifies the name of a file listing stop words. The default file name extension is .stop. The file content format is the same as that of the file for a Simple dictionary.
+
+
FILEPATH
Specifies the directory for storing dictionary definition files. The directory can be a local directory or an OBS directory. The local directory format is file://absolute_path. The OBS directory format is obs://bucket_name/path accesskey=ak secretkey=sk region=rg. The default value is the directory where predefined dictionary files are located. If any of the FILEPATH and STOPWORDS parameters is specified, the other one must also be specified.
+
+
+
The name of a dictionary definition file can contain only lowercase letters, digits, and underscores (_).
+
+
+
value
+
Specifies a parameter value. If the value is not an identifier or a number, enclose it with single quotation marks (''). You can also enclose identifiers and numbers.
+
]]>
+
+
+
Function
+
CREATE TRIGGER creates a trigger. The trigger will be associated with the specified table or view, and will execute the specified function operations are performed.
+
+
Precautions
+
Currently, triggers can be created only on ordinary row-store tables, instead of on column-store tables, temporary tables, or unlogged tables.
If multiple triggers of the same kind are defined for the same event, they will be fired in alphabetical order by name.
Triggers are usually used for data association and synchronization between multiple tables. SQL execution performance is greatly affected. Therefore, you are advised not to use this statement when a large amount of data needs to be synchronized and performance requirements are high.
+
+
Examples
+
-- Create a source table and a destination table.
+postgres=# CREATE TABLE test_trigger_src_tbl ( id1 INT , id2 INT , id3 INT ) ;
+postgres=# CREATE TABLE test_trigger_des_tbl ( id1 INT , id2 INT , id3 INT ) ;
+
+-- Create a trigger function.
+postgres=# CREATE OR REPLACE FUNCTION tri_insert_func ( ) RETURNS TRIGGER AS
+$$
+DECLARE
+BEGIN
+INSERT INTO test_trigger_des_tbl VALUES ( NEW.id1 , NEW.id2 , NEW.id3 ) ;
+RETURN NEW ;
+END
+$$ LANGUAGE PLPGSQL ;
+postgres=# CREATE OR REPLACE FUNCTION tri_update_func ( ) RETURNS TRIGGER AS
+$$
+DECLARE
+BEGIN
+UPDATE test_trigger_des_tbl SET id3 = NEW.id3 WHERE id1=OLD.id1 ;
+RETURN OLD ;
+END
+$$ LANGUAGE PLPGSQL ;
+postgres=# CREATE OR REPLACE FUNCTION TRI_DELETE_FUNC ( ) RETURNS TRIGGER AS
+$$
+DECLARE
+BEGIN
+DELETE FROM test_trigger_des_tbl WHERE id1=OLD.id1 ;
+RETURN OLD ;
+END
+$$ LANGUAGE PLPGSQL ;
+
+-- Create an INSERT trigger.
+postgres=# CREATE TRIGGER insert_trigger
+BEFORE INSERT ON test_trigger_src_tbl
+FOR EACH ROW
+EXECUTE PROCEDURE tri_insert_func ( ) ;
+
+-- Create an UPDATE trigger.
+postgres=# CREATE TRIGGER update_trigger
+AFTER UPDATE ON test_trigger_src_tbl
+FOR EACH ROW
+EXECUTE PROCEDURE tri_update_func ( ) ;
+
+-- Create a DELETE trigger.
+postgres=# CREATE TRIGGER delete_trigger
+BEFORE DELETE ON test_trigger_src_tbl
+FOR EACH ROW
+EXECUTE PROCEDURE tri_delete_func ( ) ;
+
+
Syntax
+
CREATE [ CONSTRAINT ] TRIGGER trigger_name { BEFORE | AFTER | INSTEAD OF } { event [ OR ... ] }
+ ON table_name
+ [ FROM referenced_table_name ]
+ { NOT DEFERRABLE | [ DEFERRABLE ] { INITIALLY IMMEDIATE | INITIALLY DEFERRED } }
+ [ FOR [ EACH ] { ROW | STATEMENT } ]
+ [ WHEN ( condition ) ]
+ EXECUTE PROCEDURE function_name ( arguments );
(Optional) Creates a constraint trigger. That is, the trigger is used as a constraint. This is the same as a regular trigger except that the timing of the trigger firing can be adjusted using SET CONSTRAINTS. Constraint triggers must be AFTER ROW triggers.
+
+
trigger_name
+
Specifies the name of the trigger to be created. This must be distinct from the name of any other trigger for the same table. The name cannot be schema-qualified 鈥?the trigger inherits the schema of its table. For a constraint trigger, this is also the name to use when modifying the trigger's behavior using SET CONSTRAINTS.
+
Value range: a string, which complies with the identifier naming convention and contains a maximum of 63 characters.
+
+
BEFORE
+
Specifies that the function is called before the event.
+
+
AFTER
+
Specifies that the function is called after the event. A constraint trigger can only be specified as AFTER.
+
+
INSTEAD OF
+
Specifies that the function is called instead of the event.
+
+
event
+
Specifies the event that will fire the trigger. Values are INSERT, UPDATE, DELETE, and TRUNCATE. Multiple events can be specified using OR.
+
For UPDATE events, it is possible to specify a list of columns using this syntax:
+
UPDATE OF column_name1 [, column_name2 ... ]
+
The trigger will only fire if at least one of the listed columns is mentioned as a target of the UPDATE statement. INSTEAD OF UPDATE events do not allow a list of columns.
+
+
table_name
+
Specifies the name of the table for which the trigger is created.
+
Value range: name of an existing table in the database
+
+
referenced_table_name
+
Specifies the name of another table referenced by the constraint. This option is used for foreign-key constraints. It can only be specified for constraint triggers. Because foreign keys are not supported currently, this option is not recommended for general use.
+
Value range: name of an existing table in the database
+
+
DEFERRABLE |
+
NOT DEFERRABLE
Specifies the start time of the trigger. It can only be specified for constraint triggers. They determine whether the constraint is deferrable.
FOR EACH ROW indicates that the trigger should be fired once for every row affected by the trigger event.
FOR EACH STATEMENT indicates that the trigger should be fired just once per SQL statement.
+
If neither is specified, the default is FOR EACH STATEMENT. Constraint triggers can only be marked as FOR EACH ROW.
+
+
condition
+
Specifies whether the trigger function will actually be executed. If WHEN is specified, the function will be called only when condition returns true.
+
In FOR EACH ROW triggers, the WHEN condition can refer to columns of the old and/or new row values by writing OLD.column name or NEW.column name respectively. In addition, INSERT triggers cannot refer to OLD, and DELETE triggers cannot refer to NEW.
+
INSTEAD OF triggers do not support WHEN conditions.
+
Currently, WHEN expressions cannot contain subqueries.
+
Note that for constraint triggers, evaluation of the WHEN condition is not deferred, but occurs immediately after the row update operation is performed. If the condition does not evaluate to true, then the trigger is not queued for deferred execution.
+
+
function_name
+
Specifies a user-defined function, which must be declared as taking no parameters and returning type trigger. This is executed when a trigger fires.
+
+
arguments
+
Specifies an optional comma-separated list of parameters to be provided to the function when the trigger is executed. The parameters are literal string constants. Simple names and numeric constants can also be written here, but they will all be converted to strings. Check the description of the implementation language of the trigger function to find out how these parameters can be accessed within the function.
+
The following details trigger types:
+
INSTEAD OF triggers must be marked as FOR EACH ROW and can be defined only on views.
BEFORE and AFTER triggers on a view must be marked as FOR EACH STATEMENT.
TRUNCATE triggers must be marked as FOR EACH STATEMENT.
+
+
+
Table 1 Types of triggers supported on tables and views
When
+
+
Event
+
+
Row-Level
+
+
Statement-Level
+
+
+
+
BEFORE
+
+
INSERT/UPDATE/DELETE
+
+
Tables
+
+
Tables and views
+
+
+
TRUNCATE
+
+
Not supported.
+
+
Tables
+
+
+
AFTER
+
+
INSERT/UPDATE/DELETE
+
+
Tables
+
+
Tables and views
+
+
+
TRUNCATE
+
+
Not supported.
+
+
Tables
+
+
+
INSTEAD OF
+
+
INSERT/UPDATE/DELETE
+
+
Views
+
+
Not supported.
+
+
+
TRUNCATE
+
+
Not supported.
+
+
Not supported.
+
+
+
+
+
+
+
Table 2 Special variables in PL/pgSQL functions
Variable
+
+
Description
+
+
+
+
NEW
+
+
New tuple for INSERT and UPDATE operations. This variable is NULL for DELETE operations.
+
+
+
OLD
+
+
Old tuple for UPDATE and DELETE operations. This variable is NULL for INSERT operations.
+
+
+
TG_NAME
+
+
Trigger name.
+
+
+
TG_WHEN
+
+
Trigger timing (BEFORE, AFTER, or INSTEAD OF).
+
+
+
TG_LEVEL
+
+
Trigger frequency (ROW or STATEMENT).
+
+
+
TG_OP
+
+
Trigger event (INSERT, UPDATE, DELETE, or TRUNCATE).
+
+
+
TG_RELID
+
+
OID of the table where the trigger resides.
+
+
+
TG_RELNAME
+
+
Name of the table where the trigger resides. (This variable has been replaced by TG_TABLE_NAME.)
+
+
+
TG_TABLE_NAME
+
+
Name of the table where the trigger resides.
+
+
+
TG_TABLE_SCHEMA
+
+
Schema of the table where the trigger resides.
+
+
+
TG_NARGS
+
+
Number of parameters for the trigger function.
+
+
+
TG_ARGV[]
+
+
List of parameters for the trigger function.
+
+
+
+
+
+
]]>
+
+
+
Function
+
CREATE TYPE registers a new data type for use in the current database. The user who defines a type becomes its owner. Types are designed only for row-store tables.
+
The following data types can be created: composite type, base type, shell type, and enumerated type.
+
Composite type
A composite type is specified by a list of attribute names and data types. If the data type of an attribute is collatable, the attribute's collation rule can also be specified. This is essentially the same as the row type of a table, but using CREATE TYPE avoids the need to create an actual table when all that is wanted is to define a type. A stand-alone composite type is useful as the parameter or return type of a function.
+
To create a composite type, you must have the USAGE permission on all of its attribute types.
+
Base type
You can create a base type (scalar type). Generally, these functions must be written in the underlying language.
+
Shell type
A shell type is simply a placeholder for a type to be defined later; it is created by issuing CREATE TYPE with no parameters except for the type name. Shell types are needed as forward references when base types are created.
+
Enumerated type
An enumerated type is a list of one or more quoted labels, each of which must be 1 to 64 bytes long.
+
+
+
Precautions
+
If a schema name is given then the type is created in the specified schema. Otherwise, it is created in the current schema. The type name must be distinct from the name of any existing type or domain in the same schema. (Because tables have associated data types, the type name must also be distinct from the name of any existing table in the same schema.)
+
+
Examples
+
-- Create a composite type, create a table, insert data, and make a query.
+postgres=# CREATE TYPE compfoo AS ( f1 int , f2 text ) ;
+postgres=# CREATE TABLE t1_compfoo ( a int , b compfoo ) ;
+postgres=# CREATE TABLE t2_compfoo ( a int , b compfoo ) ;
+postgres=# INSERT INTO t1_compfoo values ( 1 , ( 1 , ' demo ' ) ) ;
+postgres=# INSERT INTO t2_compfoo select * from t1_typ5 ;
+postgres=# SELECT ( b ) .f1 FROM t1_compfoo ;
+postgres=# SELECT * FROM t1_compfoo t1 join t2_compfoo t2 on ( t1.b ) .f1= ( t1.b ) .f1 ;
+
+-- Change the owner of the user-defined type compfoo1 to usr1.
+postgres=# CREATE USER usr1 PASSWORD ' Bigdata@123 ' ;
+postgres=# ALTER TYPE compfoo1 OWNER TO usr1 ;
+
+-- Create an enumerated type.
+postgres=# CREATE TYPE bugstatus AS ENUM ( ' create ' , ' modify ' , ' closed ' ) ;
+
Specifies the name (optionally schema-qualified) of the type to be created.
+
+
attribute_name
+
Specifies the name of an attribute (column) for the composite type.
+
+
data_type
+
Specifies the name of an existing data type to become a column of the composite type.
+
+
collation
+
Specifies the name of an existing collation rule to be associated with a column of the composite type.
+
]]>
+
+
+
Function
+
CREATE USER creates a user.
+
+
Precautions
+
A user created using the CREATE USER statement has the LOGIN permission by default.
A schema named after the user is automatically created in the database where the statement is executed, but not in other databases. You can run the CREATE SCHEMA statement to create such a schema for the user in other databases.
The owner of an object created by a system administrator in a schema with the same name as a common user is the common user, not the system administrator.
+
+
Syntax
+
CREATE USER user_name [ [ WITH ] option [ ... ] ] [ ENCRYPTED | UNENCRYPTED ] { PASSWORD | IDENTIFIED BY } { 'password' | DISABLE };
+
The option clause is used to configure information, including permissions and properties.
Value range: a string. It must comply with the naming convention. It can contain a maximum of 63 characters.
+
+
password
+
Specifies the login password.
+
The new password must:
+
Contain at least eight characters. This is the default length.
Differ from the username or the username spelled backward.
Contain at least three types of the following four types of characters: uppercase characters (A to Z), lowercase characters (a to z), digits (0 to 9), and special characters, including: ~!@#$%^&*()-_=+\|[{}];:,<.>/?
Be enclosed by single or double quotation marks.
+
Value range: a string
+
]]>
+
+
+
Function
+
CREATE VIEW creates a view. A view is a virtual table, not a base table. Only view definition is stored in the database and view data is not. The data is stored in a base table. If data in the base table changes, the data in the view changes accordingly. In this sense, a view is like a window through which users can know their interested data and data changes in the database.
+
+
Examples
+
-- Create a view consisting of columns whose spcname is pg_default.
+postgres=# CREATE VIEW myView AS
+SELECT * FROM pg_tablespace WHERE spcname = ' pg_default ' ;
+
You can use WITH (security_barriers) to create a relatively secure view. This prevents attackers from printing hidden base table data by using the RAISE statement of low-cost functions.
+
+
+
Parameter Description
+
+
OR REPLACE
+
Redefines the view if it already exists.
+
+
TEMP | TEMPORARY
+
Creates a temporary view.
+
+
view_name
+
Specifies the name (optionally schema-qualified) of the view to be created.
+
Value range: a string. It must comply with the naming convention.
+
+
column_name
+
Specifies an optional list of names to be used for columns of the view. If not given, the column names are deduced from the query.
+
Value range: a string. It must comply with the naming convention.
+
+
view_option_name [= view_option_value]
+
Specifies an optional parameter for a view.
+
Currently, view_option_name supports only the security_barrier parameter. This parameter is used when the view attempts to provide row-level security.
+
Value range: Boolean type, TRUE, and FALSE.
+
+
query
+
Specifies a SELECT or VALUES statement that will provide the columns and rows of the view.
+
]]>
+
+
+
Function
+
CURSOR defines a cursor to retrieve a small number of rows at a time out of a larger query.
+
To process SQL statements, the stored procedure process assigns a memory segment to store context association. Cursors are handles or pointers pointing to context regions. With cursors, stored procedures can control alterations in context regions.
+
+
Precautions
+
CURSOR is used only in transaction blocks.
Generally, CURSOR and SELECT both have text returns. Since data is stored in binary format in the system, the system needs to convert the data from the binary format to the text format. If data is returned in text format, client applications need to convert the data back to the binary format for processing. FETCH implements conversion between binary data and text data.
Binary cursors should be used carefully. Text usually occupies larger space than binary data. A binary cursor returns internal binary data, which is easier to operate. A text cursor returns text, which is easier to retrieve and therefore reduces workload on the client. As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value (in big-endian byte order).
+
+
Examples
+
-- Set up cursor1.
+postgres=# CURSOR cursor1 FOR SELECT * FROM tpcds.customer_address ORDER BY 1 ;
+
+-- Fetch the first three rows in cursor1.
+postgres=# FETCH FORWARD 3 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+1 | AAAAAAAABAAAAAAA | 18 | Jackson | Parkway | Suite 280 | Fairfield | Maricopa County | AZ | 86192 | United States | -7.00 | condo
+2 | AAAAAAAACAAAAAAA | 362 | Washington 6th | RD | Suite 80 | Fairview | Taos County | NM | 85709 | United States | -7.00 | condo
+3 | AAAAAAAADAAAAAAA | 585 | Dogwood Washington | Circle | Suite Q | Pleasant Valley | York County | PA | 12477 | United States | -5.00 | single family
+ ( 3 rows )
+
+-- Close the cursor and commit the transaction.
+postgres=# CLOSE cursor1 ;
+
+-- Set up cursor2.
+postgres=# CURSOR cursor2 FOR VALUES ( 1 , 2 ) , ( 0 , 3 ) ORDER BY 1 ;
+
+-- Fetch the first two rows in cursor2.
+postgres=# FETCH FORWARD 2 FROM cursor2 ;
+column1 | column2
+---------+---------
+0 | 3
+1 | 2
+ ( 2 rows )
+
+-- Close the cursor and commit the transaction.
+postgres=# CLOSE cursor2 ;
+
+-- Set up a WITH HOLD cursor.
+postgres=# DECLARE cursor1 CURSOR WITH HOLD FOR SELECT * FROM tpcds.customer_address ORDER BY 1 ;
+
+-- Fetch the first two rows in cursor1.
+postgres=# FETCH FORWARD 2 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+1 | AAAAAAAABAAAAAAA | 18 | Jackson | Parkway | Suite 280 | Fairfield | Maricopa County | AZ | 86192 | United States | -7.00 | condo
+2 | AAAAAAAACAAAAAAA | 362 | Washington 6th | RD | Suite 80 | Fairview | Taos County | NM | 85709 | United States | -7.00 | condo
+ ( 2 rows )
+
+-- Fetch the next row in cursor1.
+postgres=# FETCH FORWARD 1 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+3 | AAAAAAAADAAAAAAA | 585 | Dogwood Washington | Circle | Suite Q | Pleasant Valley | York County | PA | 12477 | United States | -5.00 | single family
+ ( 1 row )
+
+-- Close the cursor.
+postgres=# CLOSE cursor1 ;
+
+
Syntax
+
CURSOR cursor_name
+ [ BINARY ] [ NO SCROLL ] [ { WITH | WITHOUT } HOLD ]
+ FOR query ;
+
+
Parameter Description
+
+
cursor_name
+
Specifies the name of the cursor to be created.
+
Value range: a string. It must comply with the naming convention.
+
+
BINARY
+
Causes the cursor to return data in binary rather than in text format.
+
+
NO SCROLL
+
Specifies how the cursor retrieves rows.
+
NO SCROLL: specifies that the cursor cannot be used to retrieve rows in a nonsequential fashion.
Unspecified: Based on the query's execution plan, the system automatically determines whether the cursor can be used to retrieve rows in a nonsequential fashion.
+
+
WITH HOLD | WITHOUT HOLD
+
Specifies whether the cursor can continue to be used after the transaction that created it successfully commits.
+
WITH HOLD: The cursor can continue to be used after the transaction that created it successfully commits.
WITHOUT HOLD: The cursor cannot be used outside of the transaction that created it.
If neither WITH HOLD nor WITHOUT HOLD is specified, the default is WITHOUT HOLD.
Cross-node transactions (for example, DDL-contained transactions created in openGauss with multiple DBnode) do not support WITH HOLD.
+
+
query
+
Uses a SELECT or VALUES clause to specify the rows to be returned by the cursor.
+
Value range: SELECT or VALUES clause
+
]]>
+
+
+
Function
+
DEALLOCATE deallocates a previously prepared statement. If you do not explicitly deallocate a prepared statement, it is deallocated when the session ends.
+
The PREPARE keyword is always ignored.
+
+
Syntax
+
DEALLOCATE [ PREPARE ] { name | ALL };
+
+
Parameter Description
+
+
name
+
Specifies the name of the prepared statement to be deallocated.
+
+
ALL
+
Deallocates all prepared statements.
+
]]>
+
+
+
Function
+
DECLARE defines a cursor to retrieve a small number of rows at a time out of a larger query and can be the start of an anonymous block.
+
This section describes usage of cursors. The usage of anonymous blocks is available in BEGIN.
+
To process SQL statements, the stored procedure process assigns a memory segment to store context association. Cursors are handles or pointers pointing to context regions. With cursors, stored procedures can control alterations in context regions.
+
Generally, CURSOR and SELECT both have text returns. Since data is stored in binary format in the system, the system needs to convert the data from the binary format to the text format. If data is returned in text format, client applications need to convert the data back to the binary format for processing. FETCH implements conversion between binary data and text data.
+
+
Precautions
+
CURSOR is used only in transaction blocks.
Binary cursors should be used carefully. Text usually occupies larger space than binary data. A binary cursor returns internal binary data, which is easier to operate. A text cursor returns text, which is easier to retrieve and therefore reduces workload on the client. As an example, if a query returns a value of one from an integer column, you would get a string of 1 with a default cursor, whereas with a binary cursor you would get a 4-byte field containing the internal representation of the value (in big-endian byte order).
+
+
Syntax
+
Define a cursor.
DECLARE cursor_name [ BINARY ] [ NO SCROLL ]
+ CURSOR [ { WITH | WITHOUT } HOLD ] FOR query ;
Value range: a string. It must comply with the naming convention.
+
+
BINARY
+
Causes the cursor to return data in binary rather than in text format.
+
+
NO SCROLL
+
Specifies how the cursor retrieves rows.
+
NO SCROLL: specifies that the cursor cannot be used to retrieve rows in a nonsequential fashion.
Unspecified: Based on the query's execution plan, the system automatically determines whether the cursor can be used to retrieve rows in a nonsequential fashion.
+
+
WITH HOLD
+
WITHOUT HOLD
+
Specifies whether the cursor can continue to be used after the transaction that created it successfully commits.
+
WITH HOLD: The cursor can continue to be used after the transaction that created it successfully commits.
WITHOUT HOLD: The cursor cannot be used outside of the transaction that created it.
If neither WITH HOLD nor WITHOUT HOLD is specified, the default is WITHOUT HOLD.
+
+
query
+
Uses a SELECT or VALUES clause to specify the rows to be returned by the cursor.
+
Value range: SELECT or VALUES clause
+
+
declare_statements
+
Declares a variable, including its name and type, for example, sales_cnt int.
+
+
execution_statements
+
Specifies the statement to be executed in an anonymous block.
+
Value range: an existing function name
+
]]>
+
+
+
Function
+
DELETE deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause is absent, the effect is to delete all rows in the table. The result is a valid, but an empty table.
+
+
Precautions
+
You must have the DELETE permission on the table to delete from it, as well as the SELECT permission for any table in the USING clause or whose values are read in the condition.
For row-store tables, the DELETE operation can be used only when they have primary key constraints.
For column-store tables, the RETURNING clause is currently not supported.
+
+
Examples
+
-- Delete employees whose ca_address_sk is smaller than 14888 from the tpcds.customer_address_bak table.
+postgres=# DELETE FROM tpcds.customer_address_bak WHERE ca_address_sk < 14888 ;
+
+-- Delete all data from the tpcds.customer_address_bak table.
+postgres=# DELETE FROM tpcds.customer_address_bak ;
+Delete the tpcds.customer_address_bak table.
+postgres=# DROP TABLE tpcds.customer_address_bak ;
+
+
Syntax
+
[ WITH [ RECURSIVE ] with_query [, ...] ]
+DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
+ [ USING using_list ]
+ [ WHERE condition | WHERE CURRENT OF cursor_name ]
+ [ RETURNING { * | { output_expr [ [ AS ] output_name ] } [, ...] } ];
+
+
Parameter Description
+
+
WITH [ RECURSIVE ] with_query [, ...]
+
Specifies one or more subqueries that can be referenced by name in the main query, which is equivalent to a temporary table.
+
If RECURSIVE is specified, it allows a SELECT subquery to reference itself by name.
+
Format of with_query:
+
with_query_name [ ( column_name [, ...] ) ] AS
+
( {select | values | insert | update | delete} )
+
-- with_query_name specifies the name of the result set generated by a subquery. Such names can be used to access the subquery
+
result set.
+
鈥?column_name specifies the column name displayed in the subquery result set.
+
鈥?Each subquery can be a SELECT, VALUES, INSERT, UPDATE or DELETE statement.
+
+
ONLY
+
If ONLY is specified before the table name, matching rows are deleted from the named table only. If ONLY is not specified, matching rows are also deleted from any tables inheriting from the named table.
+
+
table_name
+
Specifies the name (optionally schema-qualified) of the target table.
+
Value range: an existing table name
+
+
alias
+
Specifies a substitute name for the target table.
+
Value range: a string. It must comply with the naming convention rule.
+
+
using_list
+
Specifies the USING clause.
+
+
condition
+
Specifies an expression that returns a Boolean value. Only rows for which this expression returns true will be deleted.
+
+
WHERE CURRENT OF cursor_name
+
This parameter is reserved.
+
+
output_expr
+
Specifies an expression to be computed and returned by the DELETE statement after each row is deleted. The expression can use any column names of the table. Write * to return all columns.
+
+
output_name
+
Specifies a name to use for a returned column.
+
Value range: a string. It must comply with the naming convention rule.
+
]]>
+
+
+
Function
+
DO executes an anonymous code block.
+
The code block is treated as though it were the body of a function with no parameters, returning void. It is parsed and executed a single time.
+
+
Precautions
+
he procedural language to be used must already have been installed into the current database by means of CREATE LANGUAGE. plpgsql is installed by default, but other languages are not.
The user must have the USAGE permission on the procedural language, or must be a system administrator if the language is untrusted.
+
+
Syntax
+
DO [ LANGUAGE lang_name ] code;
+
+
Parameter Description
+
+
lang_name
+
Specifies the name of the procedural language the code is written in. If omitted, the default is plpgsql.
+
+
code
+
Specifies the procedural language code to be executed. This must be specified as a string literal.
+
]]>
+
+
+
Function
+
DROP DATABASE deletes a database.
+
+
Precautions
+
Only the owner of a database or a system administrator has the DROP DATABASE permission.
The preinstalled POSTGRES, TEMPLATE0, and TEMPLATE1 databases are protected and therefore cannot be deleted. To check databases in the current service, run the gsql statement \l.
If any users are connected to the database, the database cannot be deleted.
DROP DATABASE cannot be executed within a transaction block.
If DROP DATABASE fails and is rolled back, run DROP DATABASE IF EXISTS again.
+
DROP DATABASE cannot be undone.
+
+
+
Examples
+
-- Reset the enable_indexscan parameter.
+postgres=# ALTER DATABASE music3 RESET enable_indexscan ;
+
Syntax
+
DROP DATABASE [ IF EXISTS ] database_name ;
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified database does not exist.
+
+
database_name
+
Specifies the name of the database to be deleted.
+
Value range: an existing database name
+
]]>
+
+
+
Function
+
DROP DATA SOURCE deletes a data source.
+
+
Examples
+
-- Delete the data source.
+postgres=# DROP DATA SOURCE ds_tst1 CASCADE ;
+
Syntax
+
DROP DATA SOURCE [IF EXISTS] src_name [CASCADE | RESTRICT];
+
+
Parameter Description
+
+
src_name
+
Specifies the name of the data source to be deleted.
+
Value range: a string. It must comply with the naming convention.
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified data source does not exist.
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects that depend on the data source.
RESTRICT: refuses to delete the data source if any objects depend on it. This is the default action.
Currently, no objects depend on data sources. Therefore, CASCADE is equivalent to RESTRICT, and they are reserved to ensure backward compatibility.
+
+
]]>
+
+
+
Function
+
DROP Directory deletes a synonym.
+
+
Precautions
+
By default, only the initial user can perform the drop operation. When enable_access_server_directory (enable_access_server_directory), users with the sysadmin permission can also perform the drop operation.
+
+
Syntax
+
DROP DIRECTORY [ IF EXISTS ] directory_name;
+
+
Parameter Description
+
+
directory_name
+
Specifies the name of the directory to be deleted.
+
Value range: an existing directory name
+
]]>
+
+
+
Function
+
DROP FUNCTION deletes a function.
+
+
Precautions
+
If a function involves operations on temporary tables, DROP FUNCTION cannot be used.
+
+
Syntax
+
DROP FUNCTION [ IF EXISTS ] function_name
+[ ( [ {[ argmode ] [ argname ] argtype} [, ...] ] ) [ CASCADE | RESTRICT ] ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified function does not exist.
+
+
function_name
+
Specifies the name of the function to be deleted.
+
Value range: an existing function name
+
+
argmode
+
Specifies the parameter mode of the function.
+
+
argname
+
Specifies the parameter name of the function.
+
+
argtype
+
Specifies the parameter type of the function.
+
]]>
+
+
+
Function
+
DROP GROUP deletes a user group.
+
DROP GROUP is an alias for DROP ROLE.
+
+
Precautions
+
DROP GROUP is an internal interface of the openGauss management tool. You are not advised to use this interface, because doing so affects openGauss.
Only the owner of an index or a system administrator has the DROP INDEX permission.
+
+
Examples
+
-- Delete an existing index.
+postgres=# DROP INDEX tpcds.ds_ship_mode_t1_index2 ;
+
Syntax
+
DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ]
+ index_name [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
CONCURRENTLY
+
Deletes an index without locking it. A normal DROP INDEX acquires exclusive lock on the table on which the index depends, blocking other accesses until the index drop can be completed. With this option, the statement does not lock the table during index deletion.
+
This parameter allows only one index name and does not support CASCADE.
+
The DROP INDEX statement can be run within a transaction, but DROP INDEX CONCURRENTLY cannot.
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified index does not exist.
+
+
index_name
+
Specifies the index name to be deleted.
+
Value range: an existing index
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects that depend on the index.
RESTRICT: refuses to delete the index if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP OWNED deletes the database objects owned by a database role.
+
+
Precautions
+
This interface will revoke the role's permissions on all objects in the current database and shared objects (databases and tablespaces).
DROP OWNED is often used to prepare for removing one or more roles. Because DROP OWNED affects only the objects in the current database, you need to run this statement in each database that contains the objects owned by the role to be removed.
Using the CASCADE option may cause this statement to recursively remove objects owned by other users.
The databases and tablespaces owned by the role will not be removed.
+
+
Syntax
+
DROP OWNED BY name [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
name
+
Specifies the role name.
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects that depend on the objects to be deleted.
RESTRICT: refuses to delete the objects if other objects depend on them. This is the default action.
+
]]>
+
+
+
Function
+
DROP ROW LEVEL SECURITY POLICY deletes a row-level access control policy from a table.
+
+
Precautions
+
Only the owner of a table or a system administrator has the DROP ROW LEVEL SECURITY POLICY permission.
+
+
Examples
+
-- Delete a row-level access control policy.
+postgres=# DROP ROW LEVEL SECURITY POLICY all_data_rls ON all_data ;
+
Syntax
+
DROP [ ROW LEVEL SECURITY ] POLICY [ IF EXISTS ] policy_name ON table_name [ CASCADE | RESTRICT ]
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified row-level access control policy does not exist.
+
+
policy_name
+
Specifies the name of the row-level access control policy to be deleted.
table_name
Specifies the name of the table containing the row-level access control policy.
+
CASCADE/RESTRICT
Currently, no objects depend on row-level access control policies. Therefore, CASCADE is equivalent to RESTRICT, and they are reserved to ensure backward compatibility.
+
+
+
]]>
+
+
+
Function
+
DROP PROCEDURE deletes a stored procedure.
+
+
Syntax
+
DROP PROCEDURE [ IF EXISTS ] procedure_name ;
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified stored procedure does not exist.
+
+
procedure_name
+
Specifies the name of the stored procedure to be deleted.
+
Value range: an existing stored procedure name
+
]]>
+
+
+
Function
+
DROP ROLE deletes a role.
+
+
Syntax
+
DROP ROLE [ IF EXISTS ] role_name [, ...];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified role does not exist.
+
+
role_name
+
Specifies the name of the role to be deleted.
+
Value range: an existing role name
+
]]>
+
+
+
Function
+
DROP SCHEMA deletes a schema from the current database.
+
+
Precautions
+
Only the owner of a schema or a system administrator has the DROP SCHEMA permission.
+
+
Examples
+
-- Delete the schema.
+postgres=# DROP SCHEMA role1 CASCADE ;
+
Syntax
+
DROP SCHEMA [ IF EXISTS ] schema_name [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified schema does not exist.
+
+
schema_name
+
Specifies the name of the schema to be deleted.
+
Value range: an existing schema name
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes all the objects contained in the schema.
RESTRICT: refuses to delete the schema if the schema contains objects. This is the default action.
+
]]>
+
+
+
Function
+
DROP SEQUENCE deletes a sequence from the current database.
+
+
Precautions
+
Only the owner of a schema or a system administrator has the DROP SEQUENCE permission.
+
+
Examples
+
-- Delete a sequence.
+postgres=# DROP SEQUENCE serial ;
+
Syntax
+
DROP SEQUENCE [ IF EXISTS ] {[schema.]sequence_name} [ , ... ] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified sequence does not exist.
+
+
name
+
Specifies the name of the sequence to be deleted.
+
+
CASCADE
+
Automatically deletes the objects that depend on the sequence.
+
+
RESTRICT
+
Refuses to delete the sequence if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP SYNONYM deletes a synonym.
+
+
Precautions
+
Only the owner of a synonym or a system administrator has the DROP SYNONYM permission.
+
+
Syntax
+
DROP SYNONYM [ IF EXISTS ] synonym_name [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified synonym does not exist.
+
+
synonym_name
+
Specifies the name (optionally schema-qualified) of the synonym to be deleted.
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects (such as views) that depend on the synonym.
RESTRICT: refuses to delete the synonym if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP TABLE deletes a table.
+
+
Precautions
+
DROP TABLE forcibly deletes the specified table and the indexes depending on the table. After the table is deleted, the functions and stored procedures that need to use this table cannot be executed. Deleting a partitioned table also deletes all partitions in the table.
+
+
Syntax
+
DROP TABLE [ IF EXISTS ]
+ { [schema.]table_name } [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified table does not exist.
+
+
schema
+
Specifies the schema name.
+
+
table_name
+
Specifies the name of the table to be deleted.
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects (such as views) that depend on the table.
RESTRICT: refuses to delete the table if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP TABLESPACE deletes a tablespace.
+
+
Precautions
+
Only the owner of a tablespace or a system administrator has the DROP TABLESPACE permission.
The tablespace to be deleted should not contain any database objects. Otherwise, an error will be reported.
DROP TABLESPACE cannot be rolled back and therefore cannot be run in transaction blocks.
During execution of DROP TABLESPACE, database queries by other sessions using \db may fail and need to be reattempted.
If DROP TABLESPACE fails to be executed, run DROP TABLESPACE IF EXISTS.
+
+
Examples
+
-- Delete the tablespace.
+postgres=# DROP TABLESPACE ds_location2 ;
+
Syntax
+
DROP TABLESPACE [ IF EXISTS ] tablespace_name;
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified tablespace does not exist.
+
+
tablespace_name
+
Specifies the name of the tablespace to be deleted.
+
Value range: an existing tablespace name
+
]]>
+
+
+
Function
+
DROP TEXT SEARCH CONFIGURATION deletes a text search configuration.
+
+
Precautions
+
Only the owner of a text search configuration has the DROP TEXT SEARCH CONFIGURATION permission.
+
+
Examples
+
-- Delete the text search configuration.
+postgres=# DROP TEXT SEARCH CONFIGURATION joe.ngram_2 ;
+
Syntax
+
DROP TEXT SEARCH CONFIGURATION [ IF EXISTS ] name [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified text search configuration does not exist.
+
+
name
+
Specifies the name (optionally schema-qualified) of the text search configuration to be deleted.
+
+
CASCADE
+
Automatically deletes the objects that depend on the text search configuration.
+
+
RESTRICT
+
Refuses to delete the text search configuration if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP TEXT SEARCH DICTIONARY deletes a full-text retrieval dictionary.
+
+
Precautions
+
Predefined dictionaries do not support the DROP operations.
Only the owner of a dictionary or a system administrator has the DROP TEXT SEARCH DICTIONARY permission.
Execute DROP...CASCADE only when necessary because this operation will delete the text search configurations that use this dictionary.
+
+
Examples
+
-- Delete the english dictionary.
+DROP TEXT SEARCH DICTIONARY english ;
+
Syntax
+
DROP TEXT SEARCH DICTIONARY [ IF EXISTS ] name [ CASCADE | RESTRICT ]
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified full-text retrieval dictionary does not exist.
+
+
name
+
Specifies the name of the dictionary to be deleted. (If you do not specify a schema name, the dictionary in the current schema will be used.)
+
Value range: an existing dictionary name
+
+
CASCADE
+
Automatically deletes the objects that depend on the full-text retrieval dictionary and other objects that depend on these objects.
+
If any text search configuration uses the dictionary, the DROP statement will fail. You can add CASCADE to delete all text search configurations and dictionaries that use this dictionary.
+
+
RESTRICT
+
Refuses to delete the full-text retrieval dictionary if any object depends on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP TRIGGER deletes a trigger.
+
+
Precautions
+
Only the owner of a trigger or a system administrator has the DROP TRIGGER permission.
+
+
Syntax
+
DROP TRIGGER [ IF EXISTS ] trigger_name ON table_name [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified trigger does not exist.
+
+
trigger_name
+
Specifies the name of the trigger to be deleted.
+
Value range: an existing trigger name
+
+
table_name
+
Specifies the name of the table containing the trigger.
+
Value range: name of the table containing the trigger
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects that depend on the trigger.
RESTRICT: refuses to delete the trigger if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP TYPE deletes a user-defined data type. Only the owner of a type has the DROP TYPE permission.
+
+
Syntax
+
DROP TYPE [ IF EXISTS ] name [, ...] [ CASCADE | RESTRICT ]
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified type does not exist.
+
+
name
+
Specifies the name (optionally schema-qualified) of the type to be deleted.
+
+
CASCADE
+
Automatically deletes the objects (such as fields, functions, and operators) that depend on the type.
+
RESTRICT
+
Refuses to delete the type if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
DROP USER deletes a user and the schema with the same name as the user.
+
+
Precautions
+
CASCADE is used to delete the objects (excluding databases) that depend on the user. CASCADE cannot delete locked objects unless the objects are unlocked or the processes locking the objects are killed.
In openGauss, the enable_kill_query configuration parameter exists in the postgresql.conf file. This parameter affects CASCADE.
If enable_kill_query is on and CASCADE is used, the statement automatically kills the processes locking dependent objects and then deletes the specified user.
If enable_kill_query is off and CASCADE is used, the statement waits until the processes locking dependent objects stop and then deletes the specified user.
+
If the dependent objects are other databases or reside in other databases, manually delete them before deleting the user from the current database. DROP USER cannot delete objects across databases.
If a data source depends on the user, the user cannot be deleted directly. You need to manually delete the data source first.
+
+
Syntax
+
DROP USER [ IF EXISTS ] user_name [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified user does not exist.
+
+
user_name
+
Specifies the name of the user to be deleted.
+
Value range: an existing username
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects that depend on the user.
RESTRICT: refuses to delete the user if any objects depend on it. This is the default action.
In openGauss, the enable_kill_query configuration parameter exists in the postgresql.conf file. This parameter affects CASCADE.
+
If enable_kill_query is on and CASCADE is used, the statement automatically kills the processes locking dependent objects and then deletes the specified user.
If enable_kill_query is off and CASCADE is used, the statement waits until the processes locking dependent objects stop and then deletes the specified user.
+
+
+
]]>
+
+
+
Function
+
DROP VIEW forcibly deletes a view from the database.
+
+
Precautions
+
Only the owner of a view or a system administrator has the DROP VIEW permission.
+
+
Examples
+
-- Delete the view.
+postgres=# DROP VIEW myView ;
+
Syntax
+
DROP VIEW [ IF EXISTS ] view_name [, ...] [ CASCADE | RESTRICT ];
+
+
Parameter Description
+
+
IF EXISTS
+
Reports a notice instead of an error if the specified view does not exist.
+
+
view_name
+
Specifies the name of the view to be deleted.
+
Value range: an existing view name
+
+
CASCADE | RESTRICT
+
CASCADE: automatically deletes the objects (such as other views) that depend on the view.
RESTRICT: refuses to delete the view if any objects depend on it. This is the default action.
+
]]>
+
+
+
Function
+
EXECUTE executes a prepared statement. Because a prepared statement exists only in the lifetime of the session, the prepared statement must be created earlier in the current session by using the PREPARE statement.
+
+
Precautions
+
If the PREPARE statement creating the prepared statement declares some parameters, the parameter set passed to the EXECUTE statement must be compatible. Otherwise, an error will occur.
+
+
Examples
+
-- Create a prepared statement for an INSERT statement and execute the prepared statement.
+postgres=# PREPARE insert_reason ( integer , character ( 16 ) , character ( 100 ) ) AS INSERT INTO tpcds.reason_t1 VALUES ( $1 , $2 , $3 ) ;
+postgres=# EXECUTE insert_reason ( 52 , ' AAAAAAAADDAAAAAA ' , ' reason 52 ' ) ;
+
+
Syntax
+
EXECUTE name [ ( parameter [, ...] ) ];
+
+
Parameter Description
+
+
name
+
Specifies the name of the prepared statement to be executed.
+
+
parameter
+
Specifies a parameter of the prepared statement. It must be of the same data type as that specified parameter in creating and generating the prepared statement.
+
]]>
+
+
+
Function
+
EXPLAIN shows the execution plan of an SQL statement.
+
The execution plan shows how the tables referenced by the statement will be scanned - by plain sequential scan, index scan, etc. - and if multiple tables are referenced, what join algorithms will be used to bring together the required rows from each input table.
+
The most critical part of the display is the estimated statement execution cost, which is the planner's guess at how long it will take to run the statement.
+
The ANALYZE option causes the statement to be actually executed, not only planned. The total elapsed time expended within each plan node (in milliseconds) and total number of rows it actually returned are added to the display. This is useful for seeing whether the planner's estimates are close to reality.
+
+
Precautions
+
The statement is actually executed when the ANALYZE option is used. If you wish to use EXPLAIN ANALYZE on an INSERT, UPDATE, DELETE, CREATE TABLE AS, or EXECUTE statement without letting the statement affect your data, use this approach:
-- Change the value of explain_perf_mode to normal.
+postgres=# SET explain_perf_mode=normal ;
+
+-- Display an execution plan for simple queries in the table.
+postgres=# EXPLAIN SELECT * FROM tpcds.customer_address_p1 ;
+QUERY PLAN
+--------------------------------------------------
+Data Node Scan ( cost=0.00..0.00 rows=0 width=0 )
+Node/s: All dbnodes
+ ( 2 rows )
+
+-- Generate an execution plan in JSON format ( with explain_perf_mode being normal ) .
+postgres=# EXPLAIN ( FORMAT JSON ) SELECT * FROM tpcds.customer_address_p1 ;
+QUERY PLAN
+--------------------------------------
+[ +
+{ +
+"Plan": { +
+"Node Type": "Data Node Scan" , +
+"Startup Cost": 0.00 , +
+"Total Cost": 0.00 , +
+"Plan Rows": 0 , +
+"Plan Width": 0 , +
+"Node/s": "All dbnodes" +
+} +
+} +
+]
+ ( 1 row )
+
+-- If there is an index and we use a query with an indexable WHERE condition, EXPLAIN might show a different plan.
+postgres=# EXPLAIN SELECT * FROM tpcds.customer_address_p1 WHERE ca_address_sk=10000 ;
+QUERY PLAN
+--------------------------------------------------
+Data Node Scan ( cost=0.00..0.00 rows=0 width=0 )
+Node/s: dn_6005_6006
+ ( 2 rows )
+
+-- Generate an execution plan in YAML format ( with explain_perf_mode being normal ) .
+postgres=# EXPLAIN ( FORMAT YAML ) SELECT * FROM tpcds.customer_address_p1 WHERE ca_address_sk=10000 ;
+QUERY PLAN
+---------------------------------
+- Plan: +
+Node Type: "Data Node Scan"+
+Startup Cost: 0.00 +
+Total Cost: 0.00 +
+Plan Rows: 0 +
+Plan Width: 0 +
+Node/s: "dn_6005_6006"
+ ( 1 row )
+
+-- Here is an example of a query plan with cost estimates suppressed:
+postgres=# EXPLAIN ( COSTS FALSE ) SELECT * FROM tpcds.customer_address_p1 WHERE ca_address_sk=10000 ;
+QUERY PLAN
+------------------------
+Data Node Scan
+Node/s: dn_6005_6006
+ ( 2 rows )
+
+-- Here is an example of a query plan for a query using an aggregate function:
+postgres=# EXPLAIN SELECT SUM ( ca_address_sk ) FROM tpcds.customer_address_p1 WHERE ca_address_sk<10000 ;
+QUERY PLAN
+---------------------------------------------------------------------------------------
+Aggregate ( cost=18.19..14.32 rows=1 width=4 )
+-> Streaming ( type: GATHER ) ( cost=18.19..14.32 rows=3 width=4 )
+Node/s: All dbnodes
+-> Aggregate ( cost=14.19..14.20 rows=3 width=4 )
+-> Seq Scan on customer_address_p1 ( cost=0.00..14.18 rows=10 width=4 )
+Filter: ( ca_address_sk < 10000 )
+ ( 6 rows )
+
+
Syntax
+
Display the execution plan of an SQL statement, which supports multiple options and has no requirements for the order of options.
Specifies whether to display actual run times and other statistics.
+
Value range:
+
TRUE (default): displays them.
FALSE: does not display them.
+
+
VERBOSE boolean
+
Specifies whether to display additional information regarding the plan.
+
Value range:
+
TRUE (default): displays them.
FALSE: does not display them.
+
+
COSTS boolean
+
Specifies whether to display the estimated total cost of each plan node, estimated number of rows, estimated width of each row.
+
Value range:
+
TRUE (default): displays them.
FALSE: does not display them.
+
+
CPU boolean
+
Specifies whether to display CPU usage.
+
Value range:
+
TRUE (default): displays it.
FALSE: does not display it.
+
+
DETAIL boolean
+
Displays information about database nodes.
+
Value range:
+
TRUE (default value): displays it.
FALSE: does not display it.
+
+
NODES boolean
+
Specifies whether to display information about the nodes executed by query.
+
Value range:
+
TRUE (default): displays it.
FALSE: does not display it.
+
+
NUM_NODES boolean
+
Specifies whether to display the number of executing nodes.
+
Value range:
+
TRUE (default value): displays it.
FALSE: does not display it.
+
+
BUFFERS boolean
+
Specifies whether to display buffer usage.
+
Value range:
+
TRUE (default): displays it.
FALSE: does not display it.
+
+
TIMING boolean
+
Specifies whether to display the actual startup time and time spent on the output node.
+
Value range:
+
TRUE (default): displays them.
FALSE: does not display them.
+
+
PLAN
+
Specifies whether to store the execution plan in PLAN_TABLE. If this parameter is set to on, the execution plan is stored in PLAN_TABLE and not displayed on the screen. Therefore, this parameter cannot be used together with other parameters when it is set to on.
+
Value range:
+
ON (default): The execution plan is stored in PLAN_TABLE and not printed on the screen. If the plan is stored successfully, "EXPLAIN SUCCESS" is returned.
OFF: The execution plan is not stored in PLAN_TABLE but is printed on the screen.
+
+
FORMAT
+
Specifies the output format.
+
Value range: TEXT, XML, JSON, and YAML
+
Default value: TEXT
+
+
PERFORMANCE
+
Prints all relevant information in execution.
+
]]>
+
+
+
Function
+
EXPLAIN PLAN saves information about an execution plan into the PLAN_TABLE table. Different from the EXPLAIN statement, EXPLAIN PLAN only saves plan information and does not print information on the screen.
+
+
Precautions
+
EXPLAIN PLAN cannot be executed on a database node.
Plan information cannot be collected for SQL statements that failed to be executed.
Data in PLAN_TABLE is in a session-level lifecycle. Sessions are isolated from users, and therefore users can only view the data of the current session and current user.
+
+
Syntax
+
EXPLAIN PLAN
+[ SET STATEMENT_ID = string ]
+FOR statement ;
+
+
Parameter Description
+
+
PLAN
+
: saves plan information into PLAN_TABLE. If information is stored successfully, "EXPLAIN SUCCESS" is returned.
+
STATEMENT_ID
+
: tags each query. The tag information will be stored in PLAN_TABLE.
If the EXPLAIN PLAN statement does not contain SET STATEMENT_ID, STATEMENT_ID is empty by default. In addition, the value of STATEMENT_ID cannot exceed 30 bytes. Otherwise, an error will be reported.
+
+
]]>
+
+
+
Function
+
FETCH retrieves rows using a previously created cursor.
+
A cursor has an associated position, which is used by FETCH. The cursor position can be before the first row of the query result, on any particular row of the result, or after the last row of the result.
+
When created, a cursor is positioned before the first row.
After fetching some rows, the cursor is positioned on the row most recently retrieved.
If FETCH runs off the end of the available rows then the cursor is left positioned after the last row, or before the first row if fetching backward.
FETCH ALL or FETCH BACKWARD ALL will always leave the cursor positioned after the last row or before the first row.
+
+
Precautions
+
If the cursor is declared with NO SCROLL, backward fetches like FETCH BACKWARD are not allowed.
The forms NEXT, PRIOR, FIRST, LAST, ABSOLUTE, and RELATIVE fetch a single row after moving the cursor appropriately. If there is no such row, an empty result is returned, and the cursor is left positioned before the first row (backward fetch) or after the last row (forward fetch) as appropriate.
The forms using FORWARD and BACKWARD retrieve the indicated number of rows moving in the forward or backward direction, leaving the cursor positioned on the last-returned row or after (backward fetch)/before (forward fetch) all rows if the count exceeds the number of rows available.
RELATIVE 0, FORWARD 0, and BACKWARD 0 all request fetching the current row without moving the cursor, that is, re-fetching the most recently fetched row. This will succeed unless the cursor is positioned before the first row or after the last row; in which case, no row is returned.
If the cursor of FETCH involves a column-store table, backward fetches like BACKWARD, PRIOR, and FIRST are not allowed.
+
+
Examples
+
-- Fetch the first three rows in cursor1.
+postgres=# FETCH FORWARD 3 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+1 | AAAAAAAABAAAAAAA | 18 | Jackson | Parkway | Suite 280 | Fairfield | Maricopa County | AZ | 86192 | United States | -7.00 | condo
+2 | AAAAAAAACAAAAAAA | 362 | Washington 6th | RD | Suite 80 | Fairview | Taos County | NM | 85709 | United States | -7.00 | condo
+3 | AAAAAAAADAAAAAAA | 585 | Dogwood Washington | Circle | Suite Q | Pleasant Valley | York County | PA | 12477 | United States | -5.00 | single family
+ ( 3 rows )
+
+-- Fetch the first two rows in cursor2.
+postgres=# FETCH FORWARD 2 FROM cursor2 ;
+column1 | column2
+---------+---------
+0 | 3
+1 | 2
+ ( 2 rows )
+
+-- Fetch the first two rows in cursor1.
+postgres=# FETCH FORWARD 2 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+1 | AAAAAAAABAAAAAAA | 18 | Jackson | Parkway | Suite 280 | Fairfield | Maricopa County | AZ | 86192 | United States | -7.00 | condo
+2 | AAAAAAAACAAAAAAA | 362 | Washington 6th | RD | Suite 80 | Fairview | Taos County | NM | 85709 | United States | -7.00 | condo
+ ( 2 rows )
+
+-- Fetch the next row in cursor1.
+postgres=# FETCH FORWARD 1 FROM cursor1 ;
+ca_address_sk | ca_address_id | ca_street_number | ca_street_name | ca_street_type | ca_suite_number | ca_city | ca_county | ca_state | ca_zip | ca_country | ca_gmt_offset | ca_location_type
+---------------+------------------+------------------+--------------------+-----------------+-----------------+-----------------+-----------------+----------+------------+---------------+---------------+----------------------
+3 | AAAAAAAADAAAAAAA | 585 | Dogwood Washington | Circle | Suite Q | Pleasant Valley | York County | PA | 12477 | United States | -5.00 | single family
+ ( 1 row )
+
+
Syntax
+
FETCH [ direction { FROM | IN } ] cursor_name;
+
The direction clause specifies optional parameters.
+
NEXT
+ | PRIOR
+ | FIRST
+ | LAST
+ | ABSOLUTE count
+ | RELATIVE count
+ | count
+ | ALL
+ | FORWARD
+ | FORWARD count
+ | FORWARD ALL
+ | BACKWARD
+ | BACKWARD count
+ | BACKWARD ALL
+
+
Parameter Description
+
+
direction_clause
+
Defines the fetch direction.
+
Value range:
+
NEXT (default value)
Fetches the next row.
+
PRIOR
Fetches the prior row.
+
FIRST
Fetches the first row of the query (same as ABSOLUTE 1).
+
LAST
Fetches the last row of the query (same as ABSOLUTE -1).
+
ABSOLUTE count
Fetches the count'th row of the query.
+
ABSOLUTE fetches are not any faster than navigating to the desired row with a relative move: the underlying implementation must traverse all the intermediate rows anyway.
+
Value range: a possibly-signed integer
+
If count is positive, the count'th row of the query will be fetched. If count is less than the current cursor position, rewind is required, which is currently not supported.
If count is negative or 0, backward scanning is required, which is currently not supported.
+
RELATIVE count
Fetches the count'th succeeding row or the count'th prior row if count is negative.
+
Value range: a possibly-signed integer
+
If count is positive, the count'th succeeding row will be fetched.
If count is negative or 0, backward scanning is required, which is currently not supported.
If the current row contains no data, RELATIVE 0 returns null.
+
count
Fetches the next count rows (same as FORWARDcount).
+
ALL
Fetches all remaining rows (same as FORWARD ALL).
+
FORWARD
Fetches the next row (same as NEXT).
+
FORWARD count
Fetches the next or prior count rows (same as RELATIVEcount).
+
FORWARD ALL
Fetches all remaining rows.
+
BACKWARD
Fetches the prior row (same as PRIOR).
+
BACKWARD count
Fetches the prior count rows (scanning backwards).
+
Value range: a possibly-signed integer
+
If count is positive, count prior rows will be fetched.
If count is a negative, count succeeding rows will be fetched.
BACKWARD 0 re-fetches the current row, if any.
+
BACKWARD ALL
Fetches all prior rows (scanning backwards).
+
+
+
{ FROM | IN } cursor_name
+
Specifies the cursor name using the keyword FROM or IN.
+
Value range: an existing cursor name
+
]]>
+
+
+
Function
+
GRANT is used to grant permissions to roles and users.
+
GRANT is used in the following scenarios:
+
Granting system permissions to roles or users
System permissions are also called user properties, including SYSADMIN, CREATEDB, CREATEROLE, AUDITADMIN, and LOGIN.
+
They can be specified only by the CREATE ROLE or ALTER ROLE statement. The SYSADMIN permissions can be granted and revoked using GRANT ALL PRIVILEGE and REVOKE ALL PRIVILEGE, respectively. System permissions cannot be inherited by a user from a role, and cannot be granted using PUBLIC.
+
Granting database object permissions to roles or users
Grant permissions related to database objects (tables, views, specified columns, databases, functions, schemas, and tablespaces) to specified roles or users.
+
GRANT gives specific permissions on a database object to one or more roles. These permissions are added to those already granted, if any.
+
The keyword PUBLIC indicates that the permissions are to be granted to all roles, including those that might be created later. PUBLIC can be thought of as an implicitly defined group that always includes all roles. Any particular role will have the sum of permissions granted directly to it, permissions granted to any role it is presently a member of, and permissions granted to PUBLIC.
+
If WITH GRANT OPTION is specified, the recipient of the permission can in turn grant it to others. Without a grant option, the recipient cannot do that. GRANT options cannot be granted to PUBLIC. Only openGauss supports this operation.
+
openGauss grants the permissions for objects of certain types to PUBLIC. By default, permissions on tables, columns, sequences, foreign data sources, foreign servers, schemas, and tablespaces are not granted to PUBLIC, but the following permissions are granted to PUBLIC: CONNECT and CREATE TEMP TABLE permissions on databases, EXECUTE permission on functions, and USAGE permission on languages and data types (including domains). An object owner can revoke the default permissions granted to PUBLIC and grant permissions to other users as needed. For security purposes, you are advised to create an object and set its permissions in the same transaction so that other users do not have time windows to use the object. In addition, you can run the ALTER DEFAULT PRIVILEGES statement to modify the default permissions.
+
Granting a role's or user's permissions to other roles or users
Grant a role's or user's permissions to one or more roles or users. In this case, every role or user can be regarded as a set of one or more database permissions.
+
If WITH ADMIN OPTION is specified, the recipients can in turn grant the permissions to other roles or users or revoke the permissions they have granted to other roles or users. If recipients' permissions are changed or revoked later, the grantees' permissions will also change.
+
Database administrators can grant or revoke permissions for any roles or users. Roles with the CREATEROLE permission can grant or revoke permissions for non-admin roles.
+
+
+
Examples
+
postgres=# CREATE USER joe PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT ALL PRIVILEGES TO joe ;
+Afterward , user joe has the sysadmin permissions.
+Example 2: Granting object permissions to a user or role
+Revoke the sysadmin permission from the joe user. Grant the usage permission of the tpcds schema and all permissions on the tpcds.reason table to joe.postgres=# REVOKE ALL PRIVILEGES FROM joe ;
+postgres=# GRANT USAGE ON SCHEMA tpcds TO joe ;
+postgres=# GRANT ALL PRIVILEGES ON tpcds.reason TO joe ;
+Then joe has all permissions on the tpcds.reason table , including create , retrieve , update , and delete.
+Grant the retrieve permission of r_reason_sk , r_reason_id , and r_reason_desc columns and the update permission of the r_reason_desc column in the tpcds.reason table to joe.postgres=# GRANT select ( r_reason_sk , r_reason_id , r_reason_desc ) , update ( r_reason_desc ) ON tpcds.reason TO joe ;
+Then joe has the retrieve permission of r_reason_sk and r_reason_id columns in the tpcds.reason table. To enable user joe to grant these permissions to other users , execute the following statement:
+postgres=# GRANT select ( r_reason_sk , r_reason_id ) ON tpcds.reason TO joe WITH GRANT OPTION ;
+Grant the postgres database connection permission and schema creation permission to user joe , and enable this user to grant these permissions to other users.
+postgres=# GRANT create , connect on database postgres TO joe WITH GRANT OPTION ;
+Create role tpcds_manager , grant the tpcds schema access permission and object creation permission to this role , but do not enable this role to grant these permissions to others.
+postgres=# CREATE ROLE tpcds_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT USAGE , CREATE ON SCHEMA tpcds TO tpcds_manager ;
+Grant all the permissions on the tpcds_tbspc tablespace to user joe but do not enable this user to grant these permissions to others.
+postgres=# CREATE TABLESPACE tpcds_tbspc RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+postgres=# GRANT ALL ON TABLESPACE tpcds_tbspc TO joe ;
+Example 3: Granting the permissions of one user or role to others
+Create role manager , grant user joe ' s permissions to the created role , and enable this role to grant its permissions to others.postgres=# CREATE ROLE manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT joe TO manager WITH ADMIN OPTION ;
+Create role senior_manager and grant manager ' s permissions to senior_manager.postgres=# CREATE ROLE senior_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT manager TO senior_manager ;
+Revoke permissions granted to senior_manager and manager and delete manager.postgres=# REVOKE manager FROM joe ;
+postgres=# REVOKE senior_manager FROM manager ;
+postgres=# DROP USER manager ;
+Example 4: Revoking permissions and deleting roles and users
+postgres=# REVOKE ALL PRIVILEGES ON tpcds.reason FROM joe ;
+postgres=# REVOKE ALL PRIVILEGES ON SCHEMA tpcds FROM joe ;
+postgres=# REVOKE ALL ON TABLESPACE tpcds_tbspc FROM joe ;
+postgres=# DROP TABLESPACE tpcds_tbspc ;
+postgres=# REVOKE USAGE , CREATE ON SCHEMA tpcds FROM tpcds_manager ;
+postgres=# DROP ROLE tpcds_manager ;
+postgres=# DROP ROLE senior_manager ;
+postgres=# DROP USER joe CASCADE ;
+
+
Syntax
+
Grant the table or view access permission to a specified user or role.
GRANT { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON { [ TABLE ] table_name [, ...]
+ | ALL TABLES IN SCHEMA schema_name [, ...] }
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
+
Grant the column access permission to a specified user or role.
GRANT { {{ SELECT | INSERT | UPDATE | REFERENCES } ( column_name [, ...] )} [, ...]
+ | ALL [ PRIVILEGES ] ( column_name [, ...] ) }
+ ON [ TABLE ] table_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the database access permission to a specified user or role.
GRANT { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON DATABASE database_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the domain access permission to a specified user or role.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON DOMAIN domain_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
The current version does not support granting the domain access permission.
+
+
Grant the external data source access permission to a specified user or role.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON FOREIGN DATA WRAPPER fdw_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the external server access permission to a specified user or role.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON FOREIGN SERVER server_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the function access permission to a specified user or role.
GRANT { EXECUTE | ALL [ PRIVILEGES ] }
+ ON { FUNCTION {function_name ( [ {[ argmode ] [ arg_name ] arg_type} [, ...] ] )} [, ...]
+ | ALL FUNCTIONS IN SCHEMA schema_name [, ...] }
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the procedural language access permission to a specified user or role.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON LANGUAGE lang_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the large object access permission to a specified user or role.
GRANT { { SELECT | UPDATE } [, ...] | ALL [ PRIVILEGES ] }
+ ON LARGE OBJECT loid [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
The current version does not support granting the large object access permission.
+
+
Grant the schema access permission to a specified user or role.
GRANT { { CREATE | USAGE } [, ...] | ALL [ PRIVILEGES ] }
+ ON SCHEMA schema_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
When granting table or view permissions to other users, you also need to grant the USAGE permission on the containing schema. Without the USAGE permission, the recipients can only see the object names, but cannot access them.
+
+
Grant the tablespace access permission to a specified user or role.
GRANT { CREATE | ALL [ PRIVILEGES ] }
+ ON TABLESPACE tablespace_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
Grant the type access permission to a specified user or role.
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON TYPE type_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
The current version does not support granting the type access permission.
+
+
Grant a role's permissions to other users or roles.
GRANT role_name [, ...]
+ TO role_name [, ...]
+ [ WITH ADMIN OPTION ];
+
Grant the sysadmin permissions to a specified role.
GRANT ALL { PRIVILEGES | PRIVILEGE }
+ TO role_name;
+
+
+
Parameter Description
+
+
SELECT
+
Allows SELECT from any column, or the specific columns listed, of the specified table, view, or sequence. The SELECT permission on the corresponding field is also required for UPDATE or DELETE.
+
+
INSERT
+
Allows INSERT of a new row into a table.
+
+
UPDATE
+
Allows UPDATE of any column of a table. Generally, UPDATE also requires the SELECT permission to query which rows need to be updated. SELECT ... FOR UPDATE and SELECT ... FOR SHARE also require this permission on at least one column, in addition to the SELECT permission.
+
+
DELETE
+
Allows DELETE of a row from a table. Generally, DELETE also requires the SELECT permission to query which rows need to be deleted.
+
+
TRUNCATE
+
Allows TRUNCATE on a table.
+
+
REFERENCES
+
Allows creation of a foreign key constraint referencing a table. This permission is required on both referencing and referenced tables. Because foreign keys are not supported currently, this option is not recommended for general use.
+
+
CREATE
+
For databases, allows new schemas to be created within the database.
For schemas, allows new objects to be created within the schema. To rename an existing object, you must own the object and have the CREATE permission on the schema of the object.
For tablespaces, allows tables to be created within the tablespace, and allows databases and schemas to be created that have the tablespace as their default tablespace.
+
+
CONNECT
+
Allows the grantee to connect to the database.
+
+
EXECUTE
+
Allows calling a function, including use of any operators that are implemented on top of the function.
+
+
USAGE
+
For procedural languages, allows use of the language for the creation of functions in that language.
For schemas, allows access to objects contained in the schema. Without this permission, it is still possible to see the object names.
For sequences, allows use of the nextval function.
For data sources, specifies access permissions or is used as ALL PRIVILEGES.
+
+
ALL PRIVILEGES
+
Grants all available permissions to a user or role at a time. Only a system administrator has the GRANT ALL PRIVILEGES permission.
+
]]>
+
+
+
Function
+
INSERT inserts new rows into a table.
+
+
Precautions
+
You must have the INSERT permission on a table in order to insert rows into it.
Use of the RETURNING clause requires the SELECT permission on all columns mentioned in RETURNING.
If ON DUPLICATE KEY UPDATE is used, you must have the SELECT and UPDATE permissions on the table and the SELECT permission on the unique constraint (primary key or unique index).
If you use the query clause to insert rows from a query, you need to have the SELECT permission on any table or column used in the query.
When you connect to a database compatible to Teradata and td_compatible_truncation is on, a long string will be automatically truncated. If later INSERT statements (not involving foreign tables) insert long strings to columns of char- and varchar-typed columns in the target table, the system will truncate the long strings to ensure no strings exceed the maximum length defined in the target table.
If inserting multi-byte character data (such as Chinese characters) to database with the character set byte encoding (SQL_ASCII, LATIN1), and the character data crosses the truncation position, the string is truncated based on its bytes instead of characters. Unexpected result will occur in tail after the truncation. If you want correct truncation result, you are advised to adopt encoding set such as UTF8, which has no character data crossing the truncation position.
+
+
+
+
Examples
+
-- Insert a record into a table.
+postgres=# INSERT INTO tpcds.reason_t2 ( r_reason_sk , r_reason_id , r_reason_desc ) VALUES ( 1 , ' AAAAAAAABAAAAAAA ' , ' reason1 ' ) ;
+
+-- Insert a record into the table, which is equivalent to the previous syntax.
+postgres=# INSERT INTO tpcds.reason_t2 VALUES ( 2 , ' AAAAAAAABAAAAAAA ' , ' reason2 ' ) ;
+
+-- Insert multiple records into the table.
+postgres=# INSERT INTO tpcds.reason_t2 VALUES ( 3 , ' AAAAAAAACAAAAAAA ' , ' reason3 ' ) , ( 4 , ' AAAAAAAADAAAAAAA ' , ' reason4 ' ) , ( 5 , ' AAAAAAAAEAAAAAAA ' , ' reason5 ' ) ;
+
+-- Insert records whose r_reason_sk in the tpcds.tpcds.reason table is less than 5.
+postgres=# INSERT INTO tpcds.reason_t2 SELECT * FROM tpcds.reason WHERE r_reason_sk <5 ;
+
+-- Insert multiple records into the table. If the records conflict, update the r_reason_id field in the conflicting row to 'BBBBBBBBCAAAAAAA'.
+postgres=# INSERT INTO tpcds.reason_t2 VALUES ( 5 , ' BBBBBBBBCAAAAAAA ' , ' reason5 ' ) , ( 6 , ' AAAAAAAADAAAAAAA ' , ' reason6 ' ) ON DUPLICATE KEY UPDATE r_reason_id = ' BBBBBBBBCAAAAAAA ' ;
+
Specifies one or more subqueries that can be referenced by name in the main query, which is equivalent to a temporary table.
+
If RECURSIVE is specified, it allows a SELECT subquery to reference itself by name.
+
The detailed format of with_query is as follows: with_query_name [ (column_name [,...]) ] AS
+
( {select | values | insert | update | delete} )
+
-- with_query_name specifies the name of the result set generated by a subquery. Such names can be used to access the subquery
+
result set.
+
鈥?column_name specifies the column name displayed in the subquery result set.
+
鈥?Each subquery can be a SELECT, VALUES, INSERT, UPDATE or DELETE statement.
+
The INSERT ON DUPLICATE KEY UPDATE statement does not support the WITH and WITH RECURSIVE clauses.
+
+
+
table_name
+
Specifies the name of the target table where data will be inserted.
+
Value range: an existing table name
+
+
column_name
+
Specifies the name of a column in the target table.
+
The column name can be qualified with a subfield name or array subscript, if needed.
Each column not present in the explicit or implicit column list will be filled with a default value, either its declared default value or NULL if there is none. Inserting into only some fields of a composite column leaves the other fields null.
The target column names column_name can be listed in any order. If no list of column names is given at all, the default is all the columns of the table in their declared order.
The target columns are the first N column names, if there are only N columns supplied by the value clause or query.
The values provided by the value clause and query are associated with the corresponding columns from left to right in the table.
+
Value range: an existing column
+
+
expression
+
Specifies an expression or a value to assign to the corresponding column.
+
In the INSERT ON DUPLICATE KEY UPDATE statement, expression can be VALUES(column_name) or EXCLUDED.column_name, indicating the value of the column_name field of the referenced conflicting rows. VALUES(column_name) cannot be nested in an expression (for example, VALUES(column_name)+1), but EXCLUDED is not limited by this restriction.
+
If single-quotation marks are inserted in a column, the single-quotation marks need to be used for escape.
If the expression for any column is not of the correct data type, automatic type conversion will be attempted. If the attempt fails, data insertion fails, and the system returns an error message.
+
+
DEFAULT
+
Specifies the default value of a field. The value is NULL if no specified default value has been assigned to it.
+
+
query
+
Specifies a query statement (SELECT statement) that uses the query result as the inserted data.
+
+
RETURNING
+
Returns the inserted rows. The syntax of the RETURNING list is identical to that of the output list of SELECT. The INSERT ON DUPLICATE KEY UPDATE statement does not support the RETURNING clause.
+
+
output_expression
+
Specifies an expression used to calculate the output result of the INSERT statement after each row is inserted.
+
Value range: The expression can use any field in the table. You can use the asterisk (*) to return all fields of the inserted row.
+
+
output_name
+
Specifies a name to use for a returned column.
+
Value range: a string. It must comply with the naming convention rule.
+
+
ON DUPLICATE KEY UPDATE
+
For a table with a unique constraint (UNIQUE INDEX or PRIMARY KEY), if the inserted data violates the unique constraint, the UPDATE clause is executed to update the conflicting rows.
+
For a table without a unique constraint, only insert is performed.
+
Triggers are not supported. The INSERT or UPDATE trigger of the target table will not be fired.
+
Deferrable unique constraints or primary keys are not supported.
+
For a table with multiple unique constraints, if the inserted data violates multiple unique constraints, the UPDATE clause is executed to update only the first conflicting row. (The check sequence is closely related to index maintenance. Generally, the conflict check is preferentially performed on the index that is created first.)
+
Distribution columns and unique index columns cannot be updated.
It does not support row-store tables.
+
]]>
+
+
+
Function
+
LOCK TABLE obtains a table-level lock.
+
openGauss always tries to select the lock mode with minimum constraints when automatically requesting a lock for a statement referenced by a table. Use LOCK if users need a more strict lock mode. For example, suppose an application runs a transaction at the Read Committed isolation level and needs to ensure that data in a table remains stable in the duration of the transaction. To achieve this, you could obtain SHARE lock mode over the table before the query. This will prevent concurrent data changes and ensure subsequent reads of the table see a stable view of committed data. It is because the SHARE lock mode conflicts with the ROW EXCLUSIVE lock acquired by writers, and your LOCK TABLE name IN SHARE MODE statement will wait until any concurrent holders of ROW EXCLUSIVE mode locks commit or roll back. Therefore, once you obtain the lock, there are no uncommitted writes outstanding; furthermore none can begin until you release the lock.
+
+
Precautions
+
LOCK TABLE is useless outside a transaction block: the lock would remain held only to the completion of the statement. If LOCK TABLE is out of any transaction block, an error is reported.
If no lock mode is specified, then ACCESS EXCLUSIVE, the most restrictive mode, is used.
LOCK TABLE ... IN ACCESS SHARE MODE requires the SELECT permission on the target table. All other forms of LOCK require table-level UPDATE and/or the DELETE permission.
There is no UNLOCK TABLE statement. Locks are always released at transaction end.
LOCK TABLE only deals with table-level locks, and so the mode names involving ROW are all misnomers. These mode names should generally be read as indicating the intention of the user to acquire row-level locks within the locked table. Also, ROW EXCLUSIVE mode is a shareable table lock. Note that all the lock modes have identical semantics so far as LOCK TABLE is concerned, differing only in the rules about which modes conflict with which. For details about the rules, see Table 1.
Specifies the name (optionally schema-qualified) of an existing table to lock.
+
Tables are locked one-by-one in the order specified in the LOCK TABLE statement.
+
Value range: an existing table name
+
+
ONLY
+
If ONLY is specified, only that table is locked. If ONLY is not specified, the table and all its sub-tables are locked.
+
+
ACCESS SHARE
+
Allows only read operations on a table. In general, any SQL statements that only read a table and do not modify it will acquire this lock mode. The SELECT statement acquires a lock of this mode on referenced tables.
+
+
ROW SHARE
+
Allows concurrent read of a table but does not allow any other operations on the table.
+
SELECT FOR UPDATE and SELECT FOR SHARE automatically acquire the ROW SHARE lock on the target table and add the ACCESS SHARE lock to other referenced tables except FOR SHARE and FOR UPDATE.
+
+
ROW EXCLUSIVE
+
Allows concurrent read of a table but does not allow modification of data in the table like ROW SHARE. UPDATE, DELETE, and INSERT automatically acquire the ROW SHARE lock on the target table and add the ACCESS SHARE lock to other referenced tables. Generally, all statements that modify table data acquire the ROW EXCLUSIVE lock for tables.
+
+
SHARE UPDATE EXCLUSIVE
+
Protects a table against concurrent schema changes and VACUUM runs.
+
Acquired by VACUUM (without FULL), ANALYZE and CREATE INDEX CONCURRENTLY statements, and some forms of ALTER TABLE.
+
+
SHARE
+
Allows concurrent queries of a table but does not allow modification of the table.
+
Acquired by CREATE INDEX (without CONCURRENTLY).
+
+
SHARE ROW EXCLUSIVE
+
Protects a table against concurrent data changes, and is self-exclusive so that only one session can hold it at a time.
+
No SQL statements automatically acquire this lock mode.
+
+
EXCLUSIVE
+
Allows concurrent queries of the target table but does not allow any other operations.
+
This mode allows only concurrent ACCESS SHARE locks; that is, only reads from the table can proceed in parallel with a transaction holding this lock mode.
+
No SQL statements automatically acquire this lock mode on user tables. However, it will be acquired on some system catalogs in case of some operations.
+
+
ACCESS EXCLUSIVE
+
Guarantees that the holder is the only transaction accessing the table in any way.
+
Acquired by the ALTER TABLE, DROP TABLE, TRUNCATE, REINDEX, CLUSTER, and VACUUM FULL statements.
+
This is also the default lock mode for LOCK TABLE statements that do not specify a mode explicitly.
+
+
NOWAIT
+
Specifies that LOCK TABLE should not wait for any conflicting locks to be released: if the specified lock(s) cannot be acquired immediately without waiting, the transaction is aborted.
+
If NOWAIT is not specified, LOCK TABLE obtains a table-level lock, waiting if necessary for any conflicting locks to be released.
+
]]>
+
+
+
Function
+
MOVE repositions a cursor without retrieving any data. MOVE works exactly like the FETCH statement, except it only repositions the cursor and does not return rows.
+
+
Examples
+
-- Skip the first three rows of cursor1.
+postgres=# MOVE FORWARD 3 FROM cursor1 ;
+
+
Syntax
+
MOVE [ direction [ FROM | IN ] ] cursor_name;
+
The direction clause specifies optional parameters.
+
NEXT
+ | PRIOR
+ | FIRST
+ | LAST
+ | ABSOLUTE count
+ | RELATIVE count
+ | count
+ | ALL
+ | FORWARD
+ | FORWARD count
+ | FORWARD ALL
+ | BACKWARD
+ | BACKWARD count
+ | BACKWARD ALL
+
+
Parameter Description
+
The parameters of MOVE and FETCH are the same. For details, see Parameter Description in FETCH.
+
On successful completion, a MOVE statement returns a tag of the form MOVE count. The count is the number of rows that a FETCH statement with the same parameters would have returned (possibly zero).
+
+
]]>
+
+
+
Function
+
MERGE INTO conditionally matches data in a target table with that in a source table. If data matches, UPDATE is executed on the target table; if data does not match, INSERT is executed. You can use this syntax to run UPDATE and INSERT at a time for convenience
+
+
Precautions
+
You have the INSERT and UPDATE permissions for the target table and the SELECT permission for the source table.
MERGE INTO cannot be executed during redistribution.
+
+
Examples
+
-- Run MERGE INTO.
+postgres=# MERGE INTO products p
+USING newproducts np
+ON ( p.product_id = np.product_id )
+WHEN MATCHED THEN
+UPDATE SET p.product_name = np.product_name , p.category = np.category WHERE p.product_name != ' play gym '
+WHEN NOT MATCHED THEN
+INSERT VALUES ( np.product_id , np.product_name , np.category ) WHERE np.category = ' books ' ;
+MERGE 4
+
+
Syntax
+
MERGE INTO table_name [ [ AS ] alias ]
+USING { { table_name | view_name } | subquery } [ [ AS ] alias ]
+ON ( condition )
+[
+ WHEN MATCHED THEN
+ UPDATE SET { column_name = { expression | DEFAULT } |
+ ( column_name [, ...] ) = ( { expression | DEFAULT } [, ...] ) } [, ...]
+ [ WHERE condition ]
+]
+[
+ WHEN NOT MATCHED THEN
+ INSERT { DEFAULT VALUES |
+ [ ( column_name [, ...] ) ] VALUES ( { expression | DEFAULT } [, ...] ) [, ...] [ WHERE condition ] }
+];
+
+
Parameter Description
+
+
INTO
+
clause
Specifies the target table that is being updated or has data being inserted. If the target table is a replication table, the default value of a column (such as auto-increment column) in the target table cannot be the volatile function. If enable_stream_operator is set to off, the target table must contain a primary key or UNIQUE and NOT NULL constraints.
+
talbe_name
Specifies the name of the target table.
+
alias
Specifies the alias of the target table.
+
Value range: a string. It must comply with the naming convention rule.
+
+
+
USING
+
clause
Specifies the source table, which can be a table, view, or subquery. If the target table is a replication table, the USING clause cannot contain non-replication tables.
+
+
ON
+
clause
Specifies the condition used to match data between the source and target tables. Columns in the condition cannot be updated.
+
+
WHEN MATCHED
+
clause
Performs UPDATE if data in the source table matches that in the target table based on the condition.
+
Distribution keys cannot be updated. System catalogs and system columns cannot be updated.
+
+
WHEN NOT MATCHED
+
clause
Performs INSERT if data in the source table does not match that in the target table based on the condition.
+
An INSERT clause can contain only one VALUES.
+
The order of WHEN MATCHED and WHEN NOT MATCHED clauses can be reversed. One of them can be used by default, but they cannot be both used at one time. Two WHEN MATCHED or WHEN NOT MATCHED clauses cannot be specified at the same time.
+
+
DEFAULT
+
Specifies the default value of a column.
+
The value is NULL if no default value is assigned to it.
+
+
WHERE condition
+
Specifies the conditions for the UPDATE and INSERT clauses. The two clauses will be executed only when the conditions are met. The default value can be used. System columns cannot be referenced in WHERE condition.
+
]]>
+
+
+
Function
+
PREPARE creates a prepared statement.
+
A prepared statement is a performance optimizing object on the server. When the PREPARE statement is executed, the specified query is parsed, analyzed, and rewritten. When EXECUTE is executed, the prepared statement is planned and executed. This avoids repetitive parsing and analysis. After the PREPARE statement is created, it exists throughout the database session. Once it is created (even if in a transaction block), it will not be deleted when a transaction is rolled back. It can only be deleted by explicitly invoking DEALLOCATE or automatically deleted when the session ends.
+
+
Examples
+
-- Create a prepared statement for an INSERT statement and execute the prepared statement.
+postgres=# PREPARE insert_reason ( integer , character ( 16 ) , character ( 100 ) ) AS INSERT INTO tpcds.reason_t1 VALUES ( $1 , $2 , $3 ) ;
+postgres=# EXECUTE insert_reason ( 52 , ' AAAAAAAADDAAAAAA ' , ' reason 52 ' ) ;
+
+
Syntax
+
PREPARE name [ ( data_type [, ...] ) ] AS statement;
+
+
Parameter Description
+
+
name
+
Specifies the name of a prepared statement. It must be unique in the session.
+
+
data_type
+
Specifies the type of an argument.
+
+
statement
+
Specifies a SELECT, INSERT, UPDATE, DELETE, MERGE INTO, or VALUES statement.
+
]]>
+
+
+
Function
+
PREPARE TRANSACTION prepares the current transaction for two-phase commit.
+
After this statement, the transaction is no longer associated with the current session; instead, its state is fully stored on disk, and there is a high probability that it can be committed successfully, even if a database crash occurs before the commit is requested.
+
Once prepared, a transaction can later be committed or rolled back with COMMIT PREPARED or ROLLBACK PREPARED, respectively. Those statements can be issued from any session, not only the one that executed the original transaction.
+
From the point of view of the issuing session, PREPARE TRANSACTION is not unlike a ROLLBACK statement: after executing it, there is no active current transaction, and the effects of the prepared transaction are no longer visible. (The effects will become visible again if the transaction is committed.)
+
If the PREPARE TRANSACTION statement fails for any reason, it becomes a ROLLBACK and the current transaction is canceled.
+
+
Precautions
+
The transaction function is maintained automatically by the database, and should be not visible to users.
When running the PREPARE TRANSACTION statement, increase the value of max_prepared_transactions in configuration file postgresql.conf. You are advised to set max_prepared_transactions to a value not less than that of max_connections so that one pending prepared transaction is available for each session.
+
+
Syntax
+
PREPARE TRANSACTION transaction_id;
+
+
Parameter Description
+
transaction_id
+
Specifies an arbitrary identifier that later identifies this transaction for COMMIT PREPARED or ROLLBACK PREPARED. The identifier must be different from those for current prepared transactions.
+
Value range: The identifier must be written as a string literal, and must be less than 200 bytes long.
+
]]>
+
+
+
Function
+
REASSIGN OWNED changes the owner of the database object.
+
REASSIGN OWNED requires that the system change owners of all the database objects owned by old_roles to new_role.
+
+
Precautions
+
REASSIGN OWNED is often executed before role deletion.
To run the REASSIGN OWNED statement, you must have the permissions of the original and target roles.
+
+
Syntax
+
REASSIGN OWNED BY old_role [, ...] TO new_role;
+
+
Parameter Description
+
+
old_role
+
Specifies the role name of the old owner.
+
+
new_role
+
Specifies the role name of the new owner.
+
]]>
+
+
+
Function
+
REINDEX rebuilds an index using the data stored in the index's table, replacing the old copy of the index.
+
There are several scenarios in which REINDEX can be used:
+
An index has become corrupted, and no longer contains valid data.
An index has become "bloated", that is, it contains many empty or nearly-empty pages.
You have altered a storage parameter (such as a fill factor) for an index, and wish that the change takes full effect.
An index build with the CONCURRENTLY option failed, leaving an "invalid" index.
+
+
+
Precautions
+
REINDEX DATABASE and REINDEX SYSTEM type cannot be performed in transaction blocks.
+
+
Examples
+
-- Rebuild a single index.
+postgres=# REINDEX INDEX tpcds.tpcds_customer_index1 ;
+
+-- Rebuild all indexes in the tpcds.customer_t1 table:
+postgres=# REINDEX TABLE tpcds.customer_t1 ;
+Delete the tpcds.customer_t1 table.
+postgres=# DROP TABLE tpcds.customer_t1 ;
+
+
Syntax
+
Rebuild a general index.
REINDEX { INDEX | [INTERNAL] TABLE | DATABASE | SYSTEM } name [ FORCE ];
+
+
Rebuild an index partition.
REINDEX { INDEX| [INTERNAL] TABLE} name
+ PARTITION partition_name [ FORCE ];
+
+
+
Parameter Description
+
+
INDEX
+
Recreates the specified index.
+
+
INTERNAL TABLE
+
Recreates the Desc table index of a column-store table or Hadoop internal table. The TOAST table (if any) of the table is reindexed as well.
+
+
TABLE
+
Recreates all indexes of a specified table. If a table has a TOAST table, the table will also be reindexed.
+
+
DATABASE
+
Recreates all indexes within the current database.
+
+
SYSTEM
+
Recreates all indexes on system catalogs within the current database. Indexes on user tables are not processed.
+
+
name
+
Specifies the name of the index, table, or database whose index needs to be recreated. Tables and indexes can be schema-qualified.
+
REINDEX DATABASE and SYSTEM can create indexes for only the current database. Therefore, name must be the same as the current database name.
+
+
+
FORCE
+
Specifies an invalid option, which will be ignored.
+
+
partition_name
+
Specifies the name of the partition or index partition to be recreated.
+
Value range:
+
If REINDEX INDEX is used, specify the name of an index partition.
If it is REINDEX TABLE, specify the name of a partition.
If it is REINDEX INTERNAL TABLE, specify the name of a partition in a column-store partitioned table.
+
]]>
+
+
+
Function
+
RELEASE SAVEPOINT destroys a savepoint previously defined in the current transaction.
+
Destroying a savepoint makes it unavailable as a rollback point, but it has no other user visible behavior. It does not undo the effects of statements executed after the savepoint was established. To do that, use ROLLBACK TO SAVEPOINT. Destroying a savepoint when it is no longer needed allows the system to reclaim some resources earlier than transaction end.
+
RELEASE SAVEPOINT also destroys all savepoints that were established after the named savepoint was established.
+
+
Precautions
+
Specifying a savepoint name that was not previously defined causes an error.
It is not possible to release a savepoint when the transaction is in an aborted state.
If multiple savepoints have the same name, only the one that was most recently defined is released.
+
+
Examples
+
-- Delete the savepoint.
+postgres=# RELEASE SAVEPOINT my_savepoint;
+
+
Syntax
+
RELEASE [ SAVEPOINT ] savepoint_name;
+
+
Parameter Description
+
savepoint_name
+
Specifies the name of the savepoint you want to destroy.
+
]]>
+
+
+
Function
+
RESET restores run-time parameters to their default values. The default values are parameter default values complied in the postgresql.conf configuration file.
+
RESET is an alternative spelling for:
+
SET configuration_parameter TO DEFAULT
+
+
Precautions
+
RESET and SET have the same transaction behavior. Their impact will be rolled back.
+
+
Examples
+
-- Reset timezone to the default value.
+postgres=# RESET timezone ;
+
+-- Set all parameters to their default values.
+postgres=# RESET ALL ;
+
+
Syntax
+
RESET {configuration_parameter | CURRENT_SCHEMA | TIME ZONE | TRANSACTION ISOLATION LEVEL | SESSION AUTHORIZATION | ALL };
+
+
Parameter Description
+
+
configuration_parameter
+
Specifies the name of a settable run-time parameter.
+
Value range: run-time parameters. You can view them by running the SHOW ALL statement.
+
+
CURRENT_SCHEMA
+
Specifies the current schema.
+
+
TIME ZONE
+
Specifies the time zone.
+
+
TRANSACTION ISOLATION LEVEL
+
Specifies the transaction isolation level.
+
+
SESSION AUTHORIZATION
+
Specifies the session authorization.
+
+
ALL
+
Resets all settable run-time parameters to default values.
+
]]>
+
+
+
Function
+
REVOKE revokes permissions from one or more roles.
+
+
Precautions
+
If a non-owner user of an object attempts to REVOKE permission on the object, the statement is executed based on the following rules:
+
If the user has no permissions whatsoever on the object, the statement will fail outright.
If an authorized user has some permissions, only the permissions with authorization options are revoked.
If the authorized user does not have the authorization option, the REVOKE ALL PRIVILEGES form will issue an error message. For other forms of statements, if the permission specified in the statement does not have the corresponding authorization option, the statement will issue a warning.
Do not perform REVOKE to a table partition. Otherwise, an alarm will be generated.
+
+
Examples
+
postgres=# CREATE USER joe PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT ALL PRIVILEGES TO joe ;
+Afterward , user joe has the sysadmin permissions.
+Example 2: Granting object permissions to a user or role
+Revoke the sysadmin permission from the joe user. Grant the usage permission of the tpcds schema and all permissions on the tpcds.reason table to joe.postgres=# REVOKE ALL PRIVILEGES FROM joe ;
+postgres=# GRANT USAGE ON SCHEMA tpcds TO joe ;
+postgres=# GRANT ALL PRIVILEGES ON tpcds.reason TO joe ;
+Then joe has all permissions on the tpcds.reason table , including create , retrieve , update , and delete.
+Grant the retrieve permission of r_reason_sk , r_reason_id , and r_reason_desc columns and the update permission of the r_reason_desc column in the tpcds.reason table to joe.postgres=# GRANT select ( r_reason_sk , r_reason_id , r_reason_desc ) , update ( r_reason_desc ) ON tpcds.reason TO joe ;
+Then joe has the retrieve permission of r_reason_sk and r_reason_id columns in the tpcds.reason table. To enable user joe to grant these permissions to other users , execute the following statement:
+postgres=# GRANT select ( r_reason_sk , r_reason_id ) ON tpcds.reason TO joe WITH GRANT OPTION ;
+Grant the postgres database connection permission and schema creation permission to user joe , and enable this user to grant these permissions to other users.
+postgres=# GRANT create , connect on database postgres TO joe WITH GRANT OPTION ;
+Create role tpcds_manager , grant the tpcds schema access permission and object creation permission to this role , but do not enable this role to grant these permissions to others.
+postgres=# CREATE ROLE tpcds_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT USAGE , CREATE ON SCHEMA tpcds TO tpcds_manager ;
+Grant all the permissions on the tpcds_tbspc tablespace to user joe but do not enable this user to grant these permissions to others.
+postgres=# CREATE TABLESPACE tpcds_tbspc RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+postgres=# GRANT ALL ON TABLESPACE tpcds_tbspc TO joe ;
+Example 3: Granting the permissions of one user or role to others
+Create role manager , grant user joe ' s permissions to the created role , and enable this role to grant its permissions to others.postgres=# CREATE ROLE manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT joe TO manager WITH ADMIN OPTION ;
+Create role senior_manager and grant manager ' s permissions to senior_manager.postgres=# CREATE ROLE senior_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT manager TO senior_manager ;
+Revoke permissions granted to senior_manager and manager and delete manager.postgres=# REVOKE manager FROM joe ;
+postgres=# REVOKE senior_manager FROM manager ;
+postgres=# DROP USER manager ;
+Example 4: Revoking permissions and deleting roles and users
+postgres=# REVOKE ALL PRIVILEGES ON tpcds.reason FROM joe ;
+postgres=# REVOKE ALL PRIVILEGES ON SCHEMA tpcds FROM joe ;
+postgres=# REVOKE ALL ON TABLESPACE tpcds_tbspc FROM joe ;
+postgres=# DROP TABLESPACE tpcds_tbspc ;
+postgres=# REVOKE USAGE , CREATE ON SCHEMA tpcds FROM tpcds_manager ;
+postgres=# DROP ROLE tpcds_manager ;
+postgres=# DROP ROLE senior_manager ;
+postgres=# DROP USER joe CASCADE ;
+
+
Syntax
+
Revoke the permission of specified table and view.
REVOKE [ GRANT OPTION FOR ]
+ { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES }[, ...]
+ | ALL [ PRIVILEGES ] }
+ ON { [ TABLE ] table_name [, ...]
+ | ALL TABLES IN SCHEMA schema_name [, ...] }
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke the permission on a specified field in a table.
REVOKE [ GRANT OPTION FOR ]
+ { {{ SELECT | INSERT | UPDATE | REFERENCES } ( column_name [, ...] )}[, ...]
+ | ALL [ PRIVILEGES ] ( column_name [, ...] ) }
+ ON [ TABLE ] table_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke permissions from a specified database.
REVOKE [ GRANT OPTION FOR ]
+ { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON DATABASE database_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke permissions on a specified function.
REVOKE [ GRANT OPTION FOR ]
+ { EXECUTE | ALL [ PRIVILEGES ] }
+ ON { FUNCTION {function_name ( [ {[ argmode ] [ arg_name ] arg_type} [, ...] ] )} [, ...]
+ | ALL FUNCTIONS IN SCHEMA schema_name [, ...] }
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke the permission on a specified large object.
REVOKE [ GRANT OPTION FOR ]
+ { { SELECT | UPDATE } [, ...] | ALL [ PRIVILEGES ] }
+ ON LARGE OBJECT loid [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revokes permissions in a specified schema.
REVOKE [ GRANT OPTION FOR ]
+ { { CREATE | USAGE } [, ...] | ALL [ PRIVILEGES ] }
+ ON SCHEMA schema_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke the permission on a specified tablespace.
REVOKE [ GRANT OPTION FOR ]
+ { CREATE | ALL [ PRIVILEGES ] }
+ ON TABLESPACE tablespace_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke permissions from a role.
REVOKE [ ADMIN OPTION FOR ]
+ role_name [, ...] FROM role_name [, ...]
+ [ CASCADE | RESTRICT ];
+
Revoke the sysadmin permission from a role.
REVOKE ALL { PRIVILEGES | PRIVILEGE } FROM role_name;
+
+
+
Parameter Description
+
The keyword PUBLIC indicates an implicitly defined group that has all roles.
+
For details about the permission types and parameters, see Parameter Description in GRANT.
+
Permissions of a role include the permissions directly granted to the role, permissions inherited from the parent role, and permissions granted to PUBLIC. Therefore, revoking the SELECT permission for an object from PUBLIC does not necessarily mean that the SELECT permission for the object has been revoked from all roles, because the SELECT permission directly granted to roles and inherited from parent roles still remains. Similarly, if the SELECT permission is revoked from a user but is not revoked from PUBLIC, the user can still run the SELECT statement.
+
If GRANT OPTION FOR is specified, the permission cannot be granted to others, but permission itself is not revoked.
+
If user A holds the UPDATE permissions on a table and the WITH GRANT OPTION and has granted them to user B, the permissions that user B holds are called dependent permissions. If the permissions or the grant option held by user A is revoked, the dependent permissions still exist. Those dependent permissions are also revoked if CASCADE is specified.
+
A user can only revoke permissions that were granted directly by that user. For example, if user A has granted permission with grant option (WITH ADMIN OPTION) to user B, and user B has in turn granted it to user C, then user A cannot revoke the permission directly from C. However, user A can revoke the grant option held by user B and use CASCADE. In this way, the permission of user C is automatically revoked. For another example, if both user A and user B have granted the same permission to C, A can revoke his own grant but not B's grant, so C will still effectively have the permission.
+
If the role executing REVOKE holds permissions indirectly via more than one role membership path, it is unspecified which containing role will be used to execute the statement. In such cases, it is best practice to use SET ROLE to become the specific role you want to do the REVOKE as, and then execute REVOKE. Failure to do so may lead to deleting permissions not intended to delete, or not deleting any permissions at all.
+
]]>
+
+
+
Function
+
ROLLBACK rolls back the current transaction and backs out all updates in the transaction.
+
ROLLBACK backs out of all changes that a transaction makes to a database if the transaction fails to be executed due to a fault.
+
+
Precautions
+
If a ROLLBACK statement is executed out of a transaction, no error occurs, but a notice is displayed.
+
+
Syntax
+
ROLLBACK [ WORK | TRANSACTION ];
+
+
Parameter Description
+
WORK | TRANSACTION
+
Specifies the optional keyword. that more clearly illustrates the syntax.
+
]]>
+
+
+
Function
+
ROLLBACK PREPARED cancels a transaction ready for two-phase committing.
+
+
Precautions
+
The function is only available in maintenance mode (when GUC parameter xc_maintenance_mode is on). Exercise caution when enabling the mode. It is used by maintenance engineers for troubleshooting. Common users should not use the mode.
Only the user that initiates a transaction or the system administrator can roll back the transaction.
The transaction function is maintained automatically by the database, and should be not visible to users.
+
+
Syntax
+
ROLLBACK PREPARED transaction_id ;
+
+
Parameter Description
+
transaction_id
+
Specifies the identifier of the transaction to be committed. The identifier must be different from those for current prepared transactions.
+
]]>
+
+
+
Function
+
ROLLBACK TO SAVEPOINT rolls back to a savepoint. It implicitly destroys all savepoints that were established after the named savepoint.
+
Rolls back all statements that were executed after the savepoint was established. The savepoint remains valid and can be rolled back to again later, if needed.
+
+
Precautions
+
Specifying a savepoint name that has not been established is an error.
Cursors have somewhat non-transactional behavior with respect to savepoints. Any cursor that is opened inside a savepoint will be closed when the savepoint is rolled back. If a previously opened cursor is affected by a FETCH or MOVE statement inside a savepoint that is later rolled back, the cursor remains at the position that FETCH left it pointing to (that is, the cursor motion caused by FETCH is not rolled back). Closing a cursor is not undone by rolling back, either. A cursor whose execution causes a transaction to abort is put in a cannot-execute state, so while the transaction can be restored using ROLLBACK TO SAVEPOINT, the cursor can no longer be used.
Use ROLLBACK TO SAVEPOINT to roll back to a savepoint. Use RELEASE SAVEPOINT to destroy a savepoint but keep the effects of the statements executed after the savepoint was established.
+
+
Examples
+
-- Undo the effects of the statements executed after my_savepoint was established:
+postgres=# START TRANSACTION ;
+postgres=# SAVEPOINT my_savepoint;
+postgres=# ROLLBACK TO SAVEPOINT my_savepoint;
+
+-- Cursor positions are not affected by savepoint rollback.
+postgres=# DECLARE foo CURSOR FOR SELECT 1 UNION SELECT 2 ;
+postgres=# SAVEPOINT foo ;
+postgres=# FETCH 1 FROM foo ;
+?column?
+----------
+1
+postgres=# ROLLBACK TO SAVEPOINT foo ;
+postgres=# FETCH 1 FROM foo ;
+?column?
+----------
+2
+postgres=# RELEASE SAVEPOINT my_savepoint;
+postgres=# COMMIT ;
+
+
Syntax
+
ROLLBACK [ WORK | TRANSACTION ] TO [ SAVEPOINT ] savepoint_name;
+
+
Parameter Description
+
savepoint_name
+
Rolls back to a savepoint.
+
]]>
+
+
+
Function
+
SAVEPOINT establishes a new savepoint within the current transaction.
+
A savepoint is a special mark inside a transaction. It allows all statements executed following its establishment to be rolled back, restoring the transaction state to what it was at the time of the savepoint.
+
+
Precautions
+
Use ROLLBACK TO SAVEPOINT to roll back to a savepoint. Use RELEASE SAVEPOINT to destroy a savepoint but keep the effects of the statements executed after the savepoint was established.
Savepoints can only be established when inside a transaction block. Multiple savepoints can be defined in a transaction.
Functions, anonymous blocks, and stored procedures do not support the SAVEPOINT syntax.
In the case of an unexpected termination of a distributed thread or process caused by a node or connection failure, or of an error caused by the inconsistency between source and destination table structures in a COPY FROM operation, the transaction cannot be rolled back to the established savepoint. Instead, the entire transaction will be rolled back.
According to the SQL standard, when a savepoint with the same name is created, the previous savepoint with the same name is automatically deleted. In openGauss, the old savepoint is retained, but only the latest one is used during rollback or release. Releasing the newer savepoint with RELEASE SAVEPOINT will cause the older one to again become accessible to ROLLBACK TO SAVEPOINT and RELEASE SAVEPOINT. In addition, SAVEPOINT fully complies with the SQL standard.
+
+
Examples
+
-- Create a savepoint.
+postgres=# SAVEPOINT my_savepoint;
+
+-- Roll back a savepoint.
+postgres=# ROLLBACK TO SAVEPOINT my_savepoint;
+
+-- Create a savepoint.
+postgres=# SAVEPOINT my_savepoint;
+
+-- Roll back a savepoint.
+postgres=# RELEASE SAVEPOINT my_savepoint;
+
+
Syntax
+
SAVEPOINT savepoint_name;
+
+
Parameter Description
+
savepoint_name
+
Specifies the name of the new savepoint.
+
]]>
+
+
+
Function
+
SELECT retrieves data from a table or view.
+
Serving as an overlaid filter for a database table, SELECT filters required data from the table using SQL keywords.
+
+
Precautions
+
You must have the SELECT permission on each field used in the SELECT statement.
+
+
Examples
+
-- Obtain the temp_t temporary table by a subquery and query all records in this table.
+postgres=# WITH temp_t ( name , isdba ) AS ( SELECT usename , usesuper FROM pg_user ) SELECT * FROM temp_t;
+
+-- Query all r_reason_sk records in the tpcds.reason table and delete duplicate records.
+postgres=# SELECT DISTINCT ( r_reason_sk ) FROM tpcds.reason ;
+
+-- Example of a LIMIT clause: Obtain a record from the table.
+postgres=# SELECT * FROM tpcds.reason LIMIT 1 ;
+
+-- Query all records and sort them in alphabetic order.
+postgres=# SELECT r_reason_desc FROM tpcds.reason ORDER BY r_reason_desc ;
+
+-- Use table aliases to obtain data from the pg_user and pg_user_status tables:
+postgres=# SELECT a.usename , b.locktime FROM pg_user a , pg_user_status b WHERE a.usesysid=b.roloid ;
+
+-- Example of the FULL JOIN clause: Join data in the pg_user and pg_user_status tables.
+postgres=# SELECT a.usename , b.locktime , a.usesuper FROM pg_user a FULL JOIN pg_user_status b on a.usesysid=b.roloid ;
+
+-- Example of the GROUP BY clause: Filter data based on query conditions, and group the results.
+postgres=# SELECT r_reason_id , AVG ( r_reason_sk ) FROM tpcds.reason GROUP BY r_reason_id HAVING AVG ( r_reason_sk ) > 25 ;
+
+-- Example of the GROUP BY CUBE clause: Filter data based on query conditions, and group the results.
+postgres=# SELECT r_reason_id , AVG ( r_reason_sk ) FROM tpcds.reason GROUP BY CUBE ( r_reason_id , r_reason_sk ) ;
+
+-- Example of the GROUP BY GROUPING SETS clause: Filter data based on query conditions, and group the results.
+postgres=# SELECT r_reason_id , AVG ( r_reason_sk ) FROM tpcds.reason GROUP BY GROUPING SETS ( ( r_reason_id , r_reason_sk ) , r_reason_sk ) ;
+
+-- Example of the UNION clause: Merge the names started with W and N in the r_reason_desc column in the tpcds.reason table.
+postgres=# SELECT r_reason_sk , tpcds.reason.r_reason_desc
+FROM tpcds.reason
+WHERE tpcds.reason.r_reason_desc LIKE ' W% '
+UNION
+SELECT r_reason_sk , tpcds.reason.r_reason_desc
+FROM tpcds.reason
+WHERE tpcds.reason.r_reason_desc LIKE ' N% ' ;
+
+-- Example of the NLS_SORT clause: Sort by Chinese Pinyin.
+postgres=# SELECT * FROM tpcds.reason ORDER BY NLSSORT ( r_reason_desc , ' NLS_SORT = SCHINESE_PINYIN_M ' ) ;
+
+-- Case-insensitive order:
+postgres=# SELECT * FROM tpcds.reason ORDER BY NLSSORT ( r_reason_desc , ' NLS_SORT = generic_m_ci ' ) ;
+
+-- Example of the PARTITION clause: Obtain data from the P_05_BEFORE partition in the tpcds.reason_p table.
+postgres=# SELECT * FROM tpcds.reason_p PARTITION ( P_05_BEFORE ) ;
+r_reason_sk | r_reason_id | r_reason_desc
+-------------+------------------+------------------------------------
+4 | AAAAAAAABAAAAAAA | reason 3
+3 | AAAAAAAABAAAAAAA | reason 1
+ ( 2 rows )
+
+-- Example of the GROUP BY clause: Group records in the tpcds.reason_p table by r_reason_id, and count the number of records in each group.
+postgres=# SELECT COUNT ( * ) , r_reason_id FROM tpcds.reason_p GROUP BY r_reason_id ;
+count | r_reason_id
+-------+------------------
+2 | AAAAAAAACAAAAAAA
+5 | AAAAAAAABAAAAAAA
+ ( 2 rows )
+
+-- Example of the GROUP BY CUBE clause: Filter data based on query conditions, and group the results.
+postgres=# SELECT * FROM tpcds.reason GROUP BY CUBE ( r_reason_id , r_reason_sk , r_reason_desc ) ;
+
+-- Example of the GROUP BY GROUPING SETS clause: Filter data based on query conditions, and group the results.
+postgres=# SELECT * FROM tpcds.reason GROUP BY GROUPING SETS ( ( r_reason_id , r_reason_sk ) , r_reason_desc ) ;
+
+-- Example of the HAVING clause: Group records in the tpcds.reason_p table by r_reason_id, count the number of records in each group, and display only values whose number of r_reason_id is greater than 2.
+postgres=# SELECT COUNT ( * ) c , r_reason_id FROM tpcds.reason_p GROUP BY r_reason_id HAVING c>2 ;
+c | r_reason_id
+
+-- Example of the IN clause: Group records in the tpcds.reason_p table by r_reason_id, count the number of records in each group, and display only the numbers of records whose r_reason_id is AAAAAAAABAAAAAAA or AAAAAAAADAAAAAAA.
+postgres=# SELECT COUNT ( * ) , r_reason_id FROM tpcds.reason_p GROUP BY r_reason_id HAVING r_reason_id IN ( ' AAAAAAAABAAAAAAA ' , ' AAAAAAAADAAAAAAA ' ) ;
+count | r_reason_id
+-------+------------------
+5 | AAAAAAAABAAAAAAA
+ ( 1 row )
+
+-- Example of the INTERSECT clause: Query records whose r_reason_id is AAAAAAAABAAAAAAA and whose r_reason_sk is smaller than 5.
+postgres=# SELECT * FROM tpcds.reason_p WHERE r_reason_id= ' AAAAAAAABAAAAAAA ' INTERSECT SELECT * FROM tpcds.reason_p WHERE r_reason_sk<5 ;
+r_reason_sk | r_reason_id | r_reason_desc
+-------------+------------------+------------------------------------
+4 | AAAAAAAABAAAAAAA | reason 3
+3 | AAAAAAAABAAAAAAA | reason 1
+ ( 2 rows )
+
+-- Example of the EXCEPT clause: Query records whose r_reason_id is AAAAAAAABAAAAAAA and whose r_reason_sk is greater than or equal to 4.
+postgres=# SELECT * FROM tpcds.reason_p WHERE r_reason_id= ' AAAAAAAABAAAAAAA ' EXCEPT SELECT * FROM tpcds.reason_p WHERE r_reason_sk<4 ;
+r_reason_sk | r_reason_id | r_reason_desc
+-------------+------------------+------------------------------------
+10 | AAAAAAAABAAAAAAA | reason 2
+10 | AAAAAAAABAAAAAAA | reason 5
+10 | AAAAAAAABAAAAAAA | reason 4
+4 | AAAAAAAABAAAAAAA | reason 3
+ ( 4 rows )
+
+-- Specify the operator ( + ) in the WHERE clause to indicate a left join.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where t1.sr_customer_sk = t2.c_customer_sk ( + )
+order by 1 desc limit 1 ;
+sr_item_sk | c_customer_id
+------------+---------------
+18000 |
+ ( 1 row )
+
+-- Specify the operator ( + ) in the WHERE clause to indicate a right join.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where t1.sr_customer_sk ( + ) = t2.c_customer_sk
+order by 1 desc limit 1 ;
+sr_item_sk | c_customer_id
+------------+------------------
+| AAAAAAAAJNGEBAAA
+ ( 1 row )
+
+-- Specify the operator ( + ) in the WHERE clause to indicate a left join and add a join condition.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where t1.sr_customer_sk = t2.c_customer_sk ( + ) and t2.c_customer_sk ( + ) < 1 order by 1 limit 1 ;
+sr_item_sk | c_customer_id
+------------+---------------
+1 |
+ ( 1 row )
+
+-- If the operator ( + ) is specified in the WHERE clause, do not use expressions connected through AND/OR.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where not ( t1.sr_customer_sk = t2.c_customer_sk ( + ) and t2.c_customer_sk ( + ) < 1 ) ;
+ERROR: Operator " ( + ) " can not be used in nesting expression.
+LINE 1: ...tomer_id from store_returns t1 , customer t2 where not ( t1.sr_...
+^
+
+-- If the operator ( + ) is specified in the WHERE clause which does not support expression macros, an error will be reported.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where ( t1.sr_customer_sk = t2.c_customer_sk ( + ) ) ::bool ;
+ERROR: Operator " ( + ) " can only be used in common expression.
+
+-- If the operator ( + ) is specified on both sides of an expression in the WHERE clause, an error will be reported.
+postgres=# select t1.sr_item_sk , t2.c_customer_id from store_returns t1 , customer t2 where t1.sr_customer_sk ( + ) = t2.c_customer_sk ( + ) ;
+ERROR: Operator " ( + ) " can ' t be specified on more than one relation in one join condition
+HINT: "t1" , "t2"...are specified Operator " ( + ) " in one condition.
+
+
Syntax
+
Query data.
+
[ WITH [ RECURSIVE ] with_query [, ...] ]
+SELECT [/*+ plan_hint */] [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
+{ * | {expression [ [ AS ] output_name ]} [, ...] }
+[ FROM from_item [, ...] ]
+[ WHERE condition ]
+[ GROUP BY grouping_element [, ...] ]
+[ HAVING condition [, ...] ]
+[ WINDOW {window_name AS ( window_definition )} [, ...] ]
+[ { UNION | INTERSECT | EXCEPT | MINUS } [ ALL | DISTINCT ] select ]
+[ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ]
+[ LIMIT { [offset,] count | ALL } ]
+[ OFFSET start [ ROW | ROWS ] ]
+[ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
+[ {FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT ]} [...] ];
+
In condition and expression, you can use the aliases of expressions in targetlist in compliance with the following rules:
+
Reference only within the same level.
Only reference aliases in targetlist.
Reference a prior expression in a subsequent expression.
The volatile function cannot be used.
The Window function cannot be used.
Aliases cannot be referenced in the join on condition.
An error is reported if targetlist contains multiple referenced aliases.
Simplified query syntax, equivalent to select * from table_name.
TABLE { ONLY {(table_name)| table_name} | table_name [ * ]};
+
+
+
Parameter Description
+
+
WITH [ RECURSIVE ] with_query [, ...]
+
Specifies one or more subqueries that can be referenced by name in the main query, which is equivalent to a temporary table.
+
If RECURSIVE is specified, it allows a SELECT subquery to reference itself by name.
+
The detailed format of with_query is as follows: with_query_name [ (column_name [, ...])] AS ({select | values | insert | update | delete})
+
with_query_name specifies the name of the result set generated by a subquery. Such names can be used to access the result sets of subqueries in a query.
column_name specifies the column name displayed in the subquery result set.
Each subquery can be a SELECT, VALUES, INSERT, UPDATE or DELETE statement.
+
+
plan_hint
+
clause
Follows the SELECT keyword in the /*+<Plan hint> */ format. It is used to optimize the plan of a SELECT statement block.
+
+
ALL
+
Specifies that all rows that meet the conditions are returned. This is the default behavior and can be omitted.
+
+
DISTINCT [ ON ( expression [, ...] ) ]
+
Removes all duplicate rows from the SELECT result set so one row is kept from each group of duplicates.
+
Retains only the first row in the set of rows that have the same result calculated on the given expression.
+
DISTINCT ON expression is explained with the same rule of ORDER BY. Unless you use ORDER BY to guarantee that the required row appears first, you cannot know what the first row is.
+
+
+
SELECT list
+
Specifies the name of a column in the table to be queried. The value can be a part of the column name or all of the column names. The wildcard (*) is used to represent the column name.
+
You may use the AS output_name clause to give an alias for an output column. The alias is used for the displaying of the output column.
+
Column names can be expressed in the following formats:
+
Manually input column names which are spaced using commas (,).
Columns computed in the FROM clause.
+
+
FROM clause
+
Specifies one or more source tables for SELECT.
+
The FROM clause can contain the following elements:
+
table_name
Specifies the name of a table or view. The schema name can be added before the table name or view name, for example, schema_name.table_name.
+
alias
Gives a temporary alias to a table to facilitate the quotation by other queries.
+
An alias is used for brevity or to eliminate ambiguity for self-joins. If an alias is provided, it completely hides the actual name of the table.
The TABLESAMPLE clause following table_name specifies that the specified sampling_method should be used to retrieve the subset of rows in the table.
+
The optional REPEATABLE clause specifies the number of seeds used to generate random numbers in the sampling method. The seed value can be any non-null constant value. If the table was not changed during the query, the two queries having the same seed and argument values will select the same sampling in this table. However, different seed values usually generate different samples. If REPEATABLE is not specified, a new random sample will be selected for each query based on the seed generated by the system.
+
column_alias
Specifies the column alias.
+
PARTITION
Queries data in the specified partition in a partitioned table.
+
partition_name
Specifies the name of a partition.
+
partition_value
Specifies the value of the specified partition key. If there are many partition keys, use the PARTITION FOR clause to specify the value of the only partition key you want to use.
+
subquery
Performs a subquery in the FROM clause. A temporary table is created to save subquery results.
+
with_query_name
Specifies that the WITH clause can also be used as the source of the FROM clause and can be referenced by the name of the WITH query.
+
function_name
Function name. Function calls can appear in the FROM clause.
+
join_type
The options are as follows:
+
[ INNER ] JOIN
A JOIN clause combines two FROM items. You can use parentheses to determine the order of nesting. In the absence of parentheses, JOIN nests left-to-right.
+
In any case, JOIN binds more tightly than the commas separating FROM items.
+
LEFT [ OUTER ] JOIN
Returns all rows that meet join conditions in the Cartesian product, plus those rows that do not match the right table rows in the left table by join conditions. This left-hand row is extended to the full width of the joined table by inserting NULL values for the right-hand columns. Note that only the JOIN clause's own condition is considered while the system decides which rows have matches. Outer conditions are applied afterward.
+
RIGHT [ OUTER ] JOIN
Returns all the joined rows, plus one row for each unmatched right-hand row (extended with NULL on the left).
+
This is just a notational convenience, since you could convert it to a LEFT OUTER JOIN by switching the left and right inputs.
+
FULL [ OUTER ] JOIN
Returns all the joined rows, pluses one row for each unmatched left-hand row (extended with NULL on the right), and pluses one row for each unmatched right-hand row (extended with NULL on the left).
+
CROSS JOIN
Is equivalent to INNER JOIN ON (TRUE), which means no rows are removed by qualification. These join types are just a notational convenience, since they do nothing you could not do with plain FROM and WHERE.
+
For the INNER and OUTER join types, a join condition must be specified, namely exactly one of NATURAL ON, join_condition, or USING (join_column [, ...]). For CROSS JOIN, none of these clauses can appear.
+
+
+
CROSS JOIN and INNER JOIN produce a simple Cartesian product, the same result as you get from listing the two items at the top level of FROM.
+
ON join_condition
Defines which rows have matches in joins. Example: ON left_table.a = right_table.a
+
USING(join_column[, ...])
ON left_table.a = right_table.a AND left_table.b = right_table.b ... abbreviation. Corresponding columns must have the same name.
+
NATURAL
Is a shorthand for a USING list that mentions all columns in the two tables that have the same names.
+
from item
Specifies the name of the query source object connected.
+
+
+
WHERE clause
+
Forms an expression for row selection to narrow down the query range of SELECT. The condition is any expression that evaluates to a result of Boolean type. Rows that do not satisfy this condition will be eliminated from the output.
+
In the WHERE clause, you can use the operator (+) to convert a table join to an outer join. However, this method is not recommended because it is not the standard SQL syntax and may raise syntax compatibility issues during platform migration. There are many restrictions on using the operator (+):
+
It can appear only in the WHERE clause.
If a table join has been specified in the FROM clause, the operator (+) cannot be used in the WHERE clause.
The operator (+) can work only on columns of tables or views, instead of on expressions.
If table A and table B have multiple join conditions, the operator (+) must be specified in all the conditions. Otherwise, the operator (+) will not take effect, and the table join will be converted into an inner join without any prompt information.
Tables specified in a join condition where the operator (+) works cannot cross queries or subqueries. If tables where the operator (+) works are not in the FROM clause of the current query or subquery, an error will be reported. If a peer table for the operator (+) does not exist, no error will be reported and the table join will be converted into an inner join.
Expressions where the operator (+) is used cannot be directly connected through OR.
If a column where the operator (+) works is compared with a constant, the expression becomes a part of the join condition.
A table cannot have multiple foreign tables.
The operator (+) can appear only in the following expressions: comparison, NOT, ANY, ALL, IN, NULLIF, IS DISTINCT FROM, and IS OF. It is not allowed in other types of expressions. In addition, these expressions cannot be connected through AND or OR.
The operator (+) can be used to convert a table join only to a left or right outer join, instead of a full join. That is, the operator (+) cannot be specified on both tables of an expression.
+
For the WHERE clause, if special character %, _, or \ is queried in LIKE, add the slash \ before each character.
+
+
+
GROUP BY clause
+
Condenses query results into a single row all selected rows that share the same values for the grouped expressions.
A CUBE grouping is an extension to the GROUP BY clause that creates subtotals for all of the possible combinations of the given list of grouping columns (or expressions). In terms of multidimensional analysis, CUBE generates all the subtotals that could be calculated for a data cube with the specified dimensions. For example, given three expressions (n=3) in the CUBE clause, the operation results in 2n = 23 = 8 groupings. Rows grouped on the values of n expressions are called regular rows, and the rest are called superaggregate rows.
+
GROUPING SETS ( grouping_element [, ...] )
Another extension to the GROUP BY clause. It allows users to specify multiple GROUP BY clauses. This improves efficiency by trimming away unnecessary data. After you specify the set of groups that you want to create using a GROUPING SETS expression within a GROUP BY clause, the database does not need to compute a whole ROLLUP or CUBE.
+
+
If the SELECT list expression quotes some ungrouped fields and no aggregate function is used, an error is displayed. This is because multiple values may be returned for ungrouped fields.
+
+
+
HAVING clause
+
Selects special groups by working with the GROUP BY clause. The HAVING clause compares some attributes of groups with a constant. Only groups that matching the logical expression in the HAVING clause are extracted.
+
+
WINDOW clause
+
The general format is WINDOW window_name AS ( window_definition ) [, ...]. window_name is a name can be referenced by window_definition. window_definition can be expressed in the following forms:
+
[ existing_window_name ]
+
[ PARTITION BY expression [, ...] ]
+
[ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST | LAST } ] [, ...] ]
+
[ frame_clause ]
+
frame_clause defines a window frame for the window function. The window function (not all window functions) depends on window frame and window frame is a set of relevant rows of the current query row. frame_clause can be expressed in the following forms:
+
[ RANGE | ROWS ] frame_start
+
[ RANGE | ROWS ] BETWEEN frame_start AND frame_end
+
frame_start and frame_end can be expressed in the following forms:
+
UNBOUNDED PRECEDING
+
value PRECEDING
+
CURRENT ROW
+
value FOLLOWING
+
UNBOUNDED FOLLOWING
+
For the query of column storage table, only row_number window function is supported, and frame_clause is not supported.
+
+
+
UNION clause
+
Computes the set union of the rows returned by the involved SELECT statements.
+
The UNION clause has the following constraints:
+
By default, the result of UNION does not contain any duplicate rows unless the ALL clause is declared.
Multiple UNION operators in the same SELECT statement are evaluated left to right, unless otherwise specified by parentheses.
FOR UPDATE cannot be specified either for a UNION result or for any input of a UNION.
+
General expression:
+
select_statement UNION [ALL] select_statement
+
select_statement can be any SELECT statement without an ORDER BY, LIMIT, FOR UPDATE, or FOR SHARE statement.
ORDER BY and LIMIT can be attached to the subexpression if it is enclosed in parentheses.
+
+
INTERSECT clause
+
Computes the set intersection of rows returned by the involved SELECT statements. The result of INTERSECT does not contain any duplicate rows.
+
The INTERSECT clause has the following constraints:
+
Multiple INTERSECT operators in the same SELECT statement are evaluated left to right, unless otherwise specified by parentheses.
Processing INTERSECT preferentially when UNION and INTERSECT operations are executed for results of multiple SELECT statements.
+
General format:
+
select_statement INTERSECT select_statement
+
select_statement can be any SELECT statement without a FOR UPDATE clause.
+
+
EXCEPT clause
+
Has the following common form:
+
select_statement EXCEPT [ ALL ] select_statement
+
select_statement can be any SELECT statement without a FOR UPDATE clause.
+
The EXCEPT operator computes the set of rows that are in the result of the left SELECT statement but not in the result of the right one.
+
The result of EXCEPT does not contain any duplicate rows unless the ALL clause is declared. To execute ALL, a row that has m duplicates in the left table and n duplicates in the right table will appear MAX(m鈥?em id="EN-US_TOPIC_0242370648__i2174037132013">n, 0) times in the result set.
+
Multiple EXCEPT operators in the same SELECT statement are evaluated left to right, unless parentheses dictate otherwise. EXCEPT binds at the same level as UNION.
+
Currently, FOR UPDATE cannot be specified either for an EXCEPT result or for any input of an EXCEPT.
+
+
MINUS clause
+
Has the same function and syntax as EXCEPT clause.
+
+
ORDER BY clause
+
Sorts data retrieved by SELECT in descending or ascending order. If the ORDER BY expression contains multiple columns:
+
If two columns are equal according to the leftmost expression, they are compared according to the next expression and so on.
If they are equal according to all specified expressions, they are returned in an implementation-dependent order.
Columns sorted by ORDER BY must be contained in the result retrieved by SELECT.
+
To support Chinese pinyin order or case-insensitive order, specify the UTF-8 or GBK encoding mode during database initiation. The statements are as follows:
OFFSET start count specifies the maximum number of rows to return, while start specifies the number of rows to skip before starting to return rows. When both are specified, start rows are skipped before starting to count the count rows to be returned.
+
+
OFFSET clause
+
The SQL: 2008 standard has introduced a different clause:
+
OFFSET start { ROW | ROWS }
+
start specifies the number of rows to skip before starting to return rows.
+
+
FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY
+
If count is omitted in a FETCH clause, it defaults to 1.
+
+
FOR UPDATE clause
+
Locks rows retrieved by SELECT. This ensures that the rows cannot be modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, or SELECT FOR UPDATE of these rows will be blocked until the current transaction ends.
+
To avoid waiting for the committing of other transactions, you can apply NOWAIT. Rows to which NOWAIT applies cannot be immediately locked. After SELECT FOR UPDATE NOWAIT is executed, an error is reported.
+
FOR SHARE behaves similarly, except that it acquires a shared rather than exclusive lock on each retrieved row. A share lock blocks other transaction from performing UPDATE, DELETE, or SELECT FOR UPDATE on these rows, but it does not prevent them from performing SELECT FOR SHARE.
+
If specified tables are named in FOR UPDATE or FOR SHARE, then only rows coming from those tables are locked. Any other tables used in SELECT are simply read as usual. Otherwise, locking all tables in the statement.
+
If FOR UPDATE or FOR SHARE is applied to a view or sub-query, it affects all tables used in the view or sub-query.
+
Multiple FOR UPDATE and FOR SHARE clauses can be written if it is necessary to specify different locking behaviors for different tables.
+
If the same table is mentioned (or implicitly affected) by both FOR UPDATE and FOR SHARE clauses, it is processed as FOR UPDATE. Similarly, a table is processed as NOWAIT if that is specified in any of the clauses affecting it.
+
The query of column-store tables does not support for update/share.
+
+
+
NLS_SORT
+
Specifies that a field is sorted in a special order. Currently, only Chinese Pinyin and case-insensitive sorting are supported.
+
Value range:
+
SCHINESE_PINYIN_M, sorted by Pinyin order. To use this sort method, specify GBK as the encoding format when you create the database. If you do not do so, this value is invalid.
generic_m_ci, case-insensitive order.
+
+
PARTITION clause
+
Queries data in the specified partition in a partitioned table.
+
]]>
+
+
+
Function
+
SELECT INTO defines a new table based on a query result and inserts data obtained by query to the new table.
+
Different from SELECT, data found by SELECT INTO is not returned to the client. The table columns have the same names and data types as the output columns of the SELECT.
+
+
Precautions
+
CREATE TABLE AS provides functions similar to SELECT INTO in functions and provides a superset of functions provided by SELECT INTO. You are advised to use CREATE TABLE AS, because SELECT INTO cannot be used in a stored procedure.
+
+
Examples
+
-- Add the values that are less than 5 in the r_reason_sk field in the tpcds.reason table to the new table.
+postgres=# SELECT * INTO tpcds.reason_t1 FROM tpcds.reason WHERE r_reason_sk < 5 ;
+INSERT 0 6
+
+
Syntax
+
[ WITH [ RECURSIVE ] with_query [, ...] ]
+SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
+ { * | {expression [ [ AS ] output_name ]} [, ...] }
+ INTO [ UNLOGGED ] [ TABLE ] new_table
+ [ FROM from_item [, ...] ]
+ [ WHERE condition ]
+ [ GROUP BY expression [, ...] ]
+ [ HAVING condition [, ...] ]
+ [ WINDOW {window_name AS ( window_definition )} [, ...] ]
+ [ { UNION | INTERSECT | EXCEPT | MINUS } [ ALL | DISTINCT ] select ]
+ [ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ]
+ [ LIMIT { count | ALL } ]
+ [ OFFSET start [ ROW | ROWS ] ]
+ [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
+ [ {FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT ]} [...] ];
+
+
Parameter Description
+
INTO [ UNLOGGED ] [ TABLE ] new_table
+
Specifies that the table is created as an unlogged table. Data written to unlogged tables is not written to the WALs, which makes them considerably faster than ordinary tables. However, they are not crash-safe: an unlogged table is automatically truncated after a crash or unclean shutdown. The contents of an unlogged table are also not replicated to standby servers. Any indexes created on an unlogged table are automatically unlogged as well.
+
new_table specifies the name of the new table.
+
For details about other SELECT INTO parameters, see Parameter Description in SELECT.
+
+
]]>
+
+
+
Function
+
SET modifies a run-time parameter.
+
+
Precautions
+
Most run-time parameters can be modified by executing SET. Some parameters cannot be modified after a server or session starts.
+
+
Examples
+
-- Set the search path of a schema.
+postgres=# SET search_path TO tpcds , public ;
+
+-- Set the date style to the traditional POSTGRES style ( date placed before month ) .
+postgres=# SET datestyle TO postgres ;
+
+
Syntax
+
Set the system time zone.
SET [ SESSION | LOCAL ] TIME ZONE { timezone | LOCAL | DEFAULT };
+
Set the schema of the table.
SET [ SESSION | LOCAL ]
+ {CURRENT_SCHEMA { TO | = } { schema | DEFAULT }
+ | SCHEMA 'schema'};
+
Set client encoding.
SET [ SESSION | LOCAL ] NAMES encoding_name;
+
Set XML parsing mode.
SET [ SESSION | LOCAL ] XML OPTION { DOCUMENT | CONTENT };
+
Set other run-time parameters.
SET [ LOCAL | SESSION ]
+ { {config_parameter { { TO | = } { value | DEFAULT }
+ | FROM CURRENT }}};
+
+
+
Parameter Description
+
+
SESSION
+
Specifies that the specified parameters take effect for the current session. This is the default value if neither SESSION nor LOCAL appears.
+
If SET or SET SESSION is executed within a transaction that is later aborted, the effects of the SET statement disappear when the transaction is rolled back. Once the surrounding transaction is committed, the effects will persist until the end of the session, unless overridden by another SET.
+
+
LOCAL
+
Specifies that the specified parameters take effect for the current transaction. After COMMIT or ROLLBACK, the session-level setting takes effect again.
+
The effects of SET LOCAL last only till the end of the current transaction, whether committed or not. A special case is SET followed by SET LOCAL within a single transaction: the SET LOCAL value will be seen until the end of the transaction, but afterward (if the transaction is committed) the SET value will take effect.
+
+
TIME ZONE timezone
+
Specifies the local time zone for the current session.
+
Value range: a valid local time zone. The corresponding run-time parameter is TimeZone. The default value is PRC.
+
+
CURRENT_SCHEMA
+
schema
+
Specifies the current schema.
+
Value range: an existing schema name
+
+
SCHEMA schema
+
Specifies the current schema. Here the schema is a string.
+
Example: set schema 'public';
+
+
NAMES encoding_name
+
Specifies the client character encoding. This statement is equivalent to set client_encoding to encoding_name.
+
Value range: a valid character encoding name. The run-time parameter corresponding to this option is client_encoding. The default encoding is SQL_ASCII.
+
+
XML OPTION option
+
Specifies the XML parsing mode.
+
Value range: CONTENT (default) and DOCUMENT
+
+
config_parameter
+
Specifies the name of a configurable run-time parameter. You can use SHOW ALL to view available run-time parameters.
+
+
value
+
Specifies the new value of config_parameter. This parameter can be specified as string constants, identifiers, numbers, or comma-separated lists of these. DEFAULT can be written to indicate resetting the parameter to its default value.
+
]]>
+
+
+
Function
+
SET CONSTRAINTS sets the behavior of constraint checking within the current transaction.
+
IMMEDIATE constraints are checked at the end of each statement. DEFERRED constraints are not checked until transaction commit. Each constraint has its own IMMEDIATE or DEFERRED mode.
+
Upon creation, a constraint is given one of three characteristics DEFERRABLE INITIALLY DEFERRED, DEFERRABLE INITIALLY IMMEDIATE, or NOT DEFERRABLE. The third class is always IMMEDIATE and is not affected by the SET CONSTRAINTS statement. The first two classes start every transaction in specified modes, but its behaviors can be changed within a transaction by SET CONSTRAINTS.
+
SET CONSTRAINTS with a list of constraint names changes the mode of just those constraints (which must all be deferrable). If multiple constraints match a name, the name is affected by all of these constraints. SET CONSTRAINTS ALL changes the modes of all deferrable constraints.
+
When SET CONSTRAINTS changes the mode of a constraint from DEFERRED to IMMEDIATE, the new mode takes effect retroactively: any outstanding data modifications that would have been checked at the end of the transaction are instead checked during the execution of the SET CONSTRAINTS statement. If any such constraint is violated, the SET CONSTRAINTS fails (and does not change the constraint mode). Therefore, SET CONSTRAINTS can be used to force checking of constraints to occur at a specific point in a transaction.
+
Check and unique constraints are always checked immediately when a row is inserted or modified.
+
+
Precautions
+
SET CONSTRAINTS sets the behavior of constraint checking only within the current transaction. Therefore, if you execute this statement outside of a transaction block (START TRANSACTION/COMMIT pair), it will not appear to have any effect.
+
+
Syntax
+
SET CONSTRAINTS { ALL | { name } [, ...] } { DEFERRED | IMMEDIATE } ;
+
+
Parameter Description
+
+
name
+
Specifies the constraint name.
+
Value range: an existing table name, which can be found in the system catalog pg_constraint.
+
+
ALL
+
Specifies all constraints.
+
+
DEFERRED
+
Specifies that constraints are not checked until transaction commit.
+
+
IMMEDIATE
+
Specifies that constraints are checked at the end of each statement.
+
]]>
+
+
+
Function
+
SET ROLE sets the current user identifier of the current session.
+
+
Precautions
+
Users of the current session must be members of specified rolename, but the system administrator can choose any roles.
Executing this statement may add rights of a user or restrict rights of a user. If the role of a session user has the INHERITS attribute, it automatically has all rights of roles that SET ROLE enables the role to be. In this case, SET ROLE physically deletes all rights directly granted to session users and rights of its belonging roles and only leaves rights of the specified roles. If the role of the session user has the NOINHERITS attribute, SET ROLE deletes rights directly granted to the session user and obtains rights of the specified role.
+
+
Examples
+
-- Set the current user to paul.
+postgres=# SET ROLE paul PASSWORD ' Bigdata@123 ' ;
+
+-- Reset the current user.
+postgres=# RESET role ;
+
+
Syntax
+
Set the current user identifier of the current session.
SET [ SESSION | LOCAL ] ROLE role_name PASSWORD 'password';
+
Reset the current user identifier to that of the current session.
RESET ROLE;
+
+
+
Parameter Description
+
+
SESSION
+
Specifies that the statement takes effect only for the current session. This parameter is used by default.
+
Value range: a string. It must comply with the naming convention rule.
+
+
LOCALE
+
Specifies that the specified statement takes effect only for the current transaction.
+
+
role_name
+
Indicates the role name.
+
Value range: a string. It must comply with the naming convention rule.
+
+
password
+
Specifies the password of a role. It must comply with the password convention.
+
+
RESET ROLE
+
Resets the current user identifier.
+
]]>
+
+
+
Function
+
SET SESSION AUTHORIZATION sets the session user identifier and the current user identifier of the current SQL session to a specified user.
+
+
Precautions
+
The session identifier can be changed only when the initial session user has the system administrator rights. Otherwise, the system supports the statement only when the authenticated user name is specified.
+
+
Examples
+
-- Set the current user to paul.
+postgres=# SET SESSION AUTHORIZATION paul password ' Bigdata@123 ' ;
+
+-- Reset the current user.
+postgres=# RESET SESSION AUTHORIZATION ;
+
+
Syntax
+
Set the session user identifier and the current user identifier of the current session.
SET [ SESSION | LOCAL ] SESSION AUTHORIZATION role_name PASSWORD 'password';
+
Reset the identifiers of the session and current users to the initially authenticated user names.
Specifies that the specified parameters take effect for the current session.
+
Value range: a string. It must comply with the naming convention rule.
+
+
LOCALE
+
Specifies that the specified statement takes effect only for the current transaction.
+
+
role_name
+
Username
+
Value range: a string. It must comply with the naming convention rule.
+
+
password
+
Specifies the password of a role. It must comply with the password convention.
+
+
DEFAULT
+
Resets the identifiers of the session and current users to the initially authenticated user names.
+
]]>
+
+
+
Function
+
SET TRANSACTION sets the characteristics of the current transaction. It has no effect on any subsequent transactions. Available transaction characteristics include the transaction isolation level and transaction access mode (read/write or read only).
+
+
Examples
+
-- Start a transaction and set its isolation level to READ COMMITTED and access mode to READ ONLY.
+postgres=# START TRANSACTION ;
+postgres=# SET LOCAL TRANSACTION ISOLATION LEVEL READ COMMITTED READ ONLY ;
+postgres=# COMMIT ;
+
+
Syntax
+
Set the isolation level and access mode of the transaction.
{ SET [ LOCAL ] TRANSACTION|SET SESSION CHARACTERISTICS AS TRANSACTION }
+ { ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE | REPEATABLE READ }
+ | { READ WRITE | READ ONLY } } [, ...]
+
+
+
Parameter Description
+
+
LOCAL
+
Specifies that the specified statement takes effect only for the current transaction.
+
+
SESSION
+
Specifies that the specified parameters take effect for the current session.
+
Value range: a string. It must comply with the naming convention.
+
+
ISOLATION_LEVEL
+
Specifies the transaction isolation level that determines the data that a transaction can view if other concurrent transactions exist.
The isolation level cannot be changed after data is modified using SELECT, INSERT, DELETE, UPDATE, FETCH, or COPY in the transaction.
+
+
+
Value range:
+
READ COMMITTED: Only submitted data is read. It is the default value.
REPEATABLE READ: Only the data committed before transaction start is read. Uncommitted data or data committed in other concurrent transactions cannot be read.
SERIALIZABLE: Currently, this isolation level is not supported in openGauss. It is equivalent to REPEATABLE READ.
+
+
READ WRITE | READ ONLY
+
Specifies the transaction access mode (read/write or read only).
+
]]>
+
+
+
Function
+
SHOW shows the current value of a run-time parameter.
+
+
Examples
+
-- Show the value of timezone.
+postgres=# SHOW timezone ;
+
+-- Show all parameters.
+postgres=# SHOW ALL ;
+
+
Syntax
+
SHOW
+ {
+ configuration_parameter |
+ CURRENT_SCHEMA |
+ TIME ZONE |
+ TRANSACTION ISOLATION LEVEL |
+ SESSION AUTHORIZATION |
+ ALL
+ };
START TRANSACTION starts a transaction. If the isolation level or read/write mode is specified, a new transaction will have those characteristics. You can also specify them using SET TRANSACTION.
+
+
Examples
+
-- Start a transaction in default mode.
+postgres=# START TRANSACTION ;
+postgres=# SELECT * FROM tpcds.reason ;
+postgres=# END ;
+
+-- Start a transaction with the isolation level being READ COMMITTED and the access mode being READ WRITE:
+postgres=# START TRANSACTION ISOLATION LEVEL READ COMMITTED READ WRITE ;
+postgres=# SELECT * FROM tpcds.reason ;
+postgres=# COMMIT ;
+
Specifies the optional keyword in BEGIN format without functions.
+
+
ISOLATION LEVEL
+
Specifies the transaction isolation level that determines the data that a transaction can view if other concurrent transactions exist.
+
The isolation level of a transaction cannot be reset after the first clause (SELECT, INSERT, DELETE, UPDATE, FETCH, COPY) for modifying data is executed in the transaction.
+
+
Value range:
+
READ COMMITTED: Only submitted data is read. It is the default value.
REPEATABLE READ: Only the data committed before transaction start is read. Uncommitted data or data committed in other concurrent transactions cannot be read.
SERIALIZABLE: Currently, this isolation level is not supported in openGauss. It is equivalent to REPEATABLE READ.
+
+
READ WRITE | READ ONLY
+
Specifies the transaction access mode (read/write or read only).
+
]]>
+
+
+
Function
+
TRUNCATE quickly removes all rows from a database table.
+
It has the same effect as an unqualified DELETE on each table, but it is faster since it does not actually scan the tables. This is most useful on large tables.
+
+
Precautions
+
TRUNCATE TABLE has the same function as a DELETE statement with no WHERE clause, emptying a table.
TRUNCATE TABLE uses less system and transaction log resources as compared with DELETE.
DELETE deletes a row each time, and records the deletion of each row in the transaction log.
TRUNCATE TABLE deletes all rows in a table by releasing the data page storing the table data, and records the releasing of the data page only in the transaction log.
+
The differences between TRUNCATE, DELETE, and DROP are as follows:
TRUNCATE TABLE deletes content, releases space, but does not delete definitions.
DELETE TABLE deletes content, but does not delete definitions nor release space.
DROP TABLE deletes content and definitions, and releases space.
ALTER TABLE [ IF EXISTS ] { [ ONLY ] table_name
+ | table_name *
+ | ONLY ( table_name ) }
+ TRUNCATE PARTITION { partition_name
+ | FOR ( partition_value [, ...] ) } ;
+
+
Parameter Description
+
+
ONLY
+
If ONLY is specified, only the specified table is cleared. Otherwise, the table and all its subtables (if any) are cleared.
+
+
table_name
+
Specifies the name (optionally schema-qualified) of the target table.
+
Value range: an existing table name
+
+
CONTINUE IDENTITY
+
Does not change the values of sequences. This is the default action.
+
+
CASCADE | RESTRICT
+
CASCADE: clears all tables that are added to a group.
RESTRICT (default value): clears all data.
+
+
partition_name
+
Specifies the partition in the target partitioned table.
+
Value range: an existing table name
+
+
partition_value
+
Specifies the value of the specified partition key.
+
The value specified by PARTITION FOR can uniquely identify a partition.
+
Value range: value range of the partition key for the partition to be renamed
+
When the PARTITION FOR clause is used, the entire partition where partition_value is located is cleared.
+
+
]]>
+
+
+
Function
+
UPDATE updates data in a table. UPDATE changes the values of the specified columns in all rows that satisfy the condition. The WHERE clause clarifies conditions. The columns to be modified need to be mentioned in the SET clause; columns not explicitly modified retain their previous values.
+
+
Precautions
+
You must have the UPDATE permission on a table to be updated.
You must have the SELECT permission on all tables involved in the expressions or conditions.
For column-store tables, the RETURNING clause is currently not supported.
Column-store tables do not support non-deterministic update. If you update data in one row with multiple rows of data in a column-store table, an error will be reported.
Memory space that records update operations in column-store tables is not reclaimed. You need to clean it by executing VACUUM FULL table_name.
Currently, UPDATE cannot be used in column-store replication tables.
+
+
Examples
+
-- Update the values of all records.
+postgres=# UPDATE student1 SET classno = classno*2 ;
+
+
Syntax
+
UPDATE [ ONLY ] table_name [ * ] [ [ AS ] alias ]
+SET {column_name = { expression | DEFAULT }
+ |( column_name [, ...] ) = {( { expression | DEFAULT } [, ...] ) |sub_query }}[, ...]
+ [ FROM from_list] [ WHERE condition ]
+ [ RETURNING {*
+ | {output_expression [ [ AS ] output_name ]} [, ...] }];
+
+where sub_query can be:
+SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
+{ * | {expression [ [ AS ] output_name ]} [, ...] }
+[ FROM from_item [, ...] ]
+[ WHERE condition ]
+[ GROUP BY grouping_element [, ...] ]
+[ HAVING condition [, ...] ]
+
+
Parameter Description
+
+
table_name
+
Specifies the name (optionally schema-qualified) of the table to be updated.
+
Value range: an existing table name
+
+
alias
+
Specifies a substitute name for the target table.
+
Value range: a string. It must comply with the naming convention rule.
+
+
column_name
+
Specifies the name of the column to be modified.
+
You can refer to this column by specifying the target table alias and the column name. For example:
+
UPDATE foo AS f SET f.col_name = 'postgres';
+
Value range: an existing column
+
+
expression
+
Specifies a value assigned to a column or an expression that assigns the value.
+
+
DEFAULT
+
Specifies the default value of a column.
+
The value is NULL if no specified default value has been assigned to it.
+
+
sub_query
+
Specifies a subquery.
+
This statement can be executed to update a table with information for other tables in the same database. For details about clauses in the SELECT statement, see SELECT.
+
+
from_list
+
Specifies a list of table expressions, allowing columns from other tables to appear in the WHERE condition and the update expressions. This is similar to the list of tables that can be specified in the FROM clause of a SELECT statement.
+
Note that the target table must not appear in the from_list, unless you intend a self-join (in which case it must appear with an alias in the from_list).
+
+
+
condition
+
Specifies an expression that returns a value of type Boolean. Only rows for which this expression returns true are updated.
+
+
output_expression
+
Specifies an expression to be computed and returned by the UPDATE statement after each row is updated.
+
Value range: The expression can use any column names of the table named by table_name or table(s) listed in FROM. Write * to return all columns.
--设置music数据库的连接数为10。
+postgres=# ALTER DATABASE music CONNECTION LIMIT= 10 ;
+
+--将music名称改为music4。
+postgres=# ALTER DATABASE music RENAME TO music4 ;
+
+--将数据库music2的所属者改为tom。
+postgres=# ALTER DATABASE music2 OWNER TO tom ;
+
+--设置music3的表空间为PG_DEFAULT。
+postgres=# ALTER DATABASE music3 SET TABLESPACE PG_DEFAULT ;
+
+--关闭在数据库music3上缺省的索引扫描。
+postgres=# ALTER DATABASE music3 SET enable_indexscan TO off ;
+
+--重置enable_indexscan参数。
+postgres=# ALTER DATABASE music3 RESET enable_indexscan ;
+
+
语法格式
+
修改数据库的最大连接数。
ALTER DATABASE database_name
+ [ [ WITH ] CONNECTION LIMIT connlimit ];
+
修改数据库名称。
ALTER DATABASE database_name
+ RENAME TO new_name;
+
修改数据库所属者。
ALTER DATABASE database_name
+ OWNER TO new_owner;
+
修改数据库默认表空间。
ALTER DATABASE database_name
+ SET TABLESPACE new_tablespace;
+
修改数据库指定会话参数值。
ALTER DATABASE database_name
+ SET configuration_parameter { { TO | = } { value | DEFAULT } | FROM CURRENT };
+
数据库配置参数重置。
ALTER DATABASE database_name RESET
+ { configuration_parameter | ALL };
--修改名称。
+postgres=# ALTER DATA SOURCE ds_test1 RENAME TO ds_test;
+
+--修改属主。
+postgres=# CREATE USER user_test1 IDENTIFIED BY ' Gs@123456 ' ;
+postgres=# ALTER USER user_test1 WITH SYSADMIN ;
+postgres=# ALTER DATA SOURCE ds_test OWNER TO user_test1 ;
+
+--修改TYPE和VERSION。
+postgres=# ALTER DATA SOURCE ds_test TYPE ' MPPDB_TYPE ' VERSION ' XXX ' ;
+
+--添加字段。
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( add dsn ' gaussdb ' , username ' test_user ' ) ;
+
+--修改字段。
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( set dsn ' unknown ' ) ;
+
+--删除字段。
+postgres=# ALTER DATA SOURCE ds_test OPTIONS ( drop username ) ;
+
+
语法格式
+
ALTER DATA SOURCE src_name
+ [TYPE 'type_str']
+ [VERSION {'version_str' | NULL}]
+ [OPTIONS ( {[ ADD | SET | DROP ] optname ['optvalue']} [, ...] )];
+ALTER DATA SOURCE src_name RENAME TO src_new_name;
+ALTER DATA SOURCE src_name OWNER TO new_owner;
--将创建在模式tpcds里的所有表（和视图）的SELECT权限授予每一个用户。
+postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA tpcds GRANT SELECT ON TABLES TO PUBLIC ;
+
+--将tpcds下的所有表的插入权限授予用户jack。
+postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA tpcds GRANT INSERT ON TABLES TO jack ;
+
+--撤销上述权限。
+postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA tpcds REVOKE SELECT ON TABLES FROM PUBLIC ;
+postgres=# ALTER DEFAULT PRIVILEGES IN SCHEMA tpcds REVOKE INSERT ON TABLES FROM jack ;
+
+
语法格式
+
ALTER DEFAULT PRIVILEGES
+ [ FOR { ROLE | USER } target_role [, ...] ]
+ [ IN SCHEMA schema_name [, ...] ]
+ abbreviated_grant_or_revoke;
ALTER GROUP是ALTER ROLE的别名，非SQL标准语法，不推荐使用，建议用户直接使用ALTER ROLE替代。
+
+
示例
+
--向用户组中添加用户。
+postgres=# ALTER GROUP super_users ADD USER lche , jim ;
+
+--从用户组中删除用户。
+postgres=# ALTER GROUP super_users DROP USER jim ;
+
+--修改用户组的名称。
+postgres=# ALTER GROUP super_users RENAME TO normal_users ;
+
+
语法格式
+
向用户组中添加用户。
ALTER GROUP group_name
+ ADD USER user_name [, ... ];
+
+
从用户组中删除用户。
ALTER GROUP group_name
+ DROP USER user_name [, ... ];
--重命名一个现有的索引。
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index1 RENAME TO ds_ship_mode_t1_index5 ;
+
+--设置索引不可用。
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index2 UNUSABLE ;
+
+--重建索引。
+postgres=# ALTER INDEX tpcds.ds_ship_mode_t1_index2 REBUILD ;
+
+--修改分区表索引CA_ADDRESS_SK_index2的表空间为example1。
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 MOVE PARTITION CA_ADDRESS_SK_index2 TABLESPACE example1 ;
+
+--修改分区表索引CA_ADDRESS_SK_index3的表空间为example2。
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 MOVE PARTITION CA_ADDRESS_SK_index3 TABLESPACE example2 ;
+
+--重命名分区表索引。
+postgres=# ALTER INDEX tpcds.ds_customer_address_p1_index2 RENAME PARTITION CA_ADDRESS_SK_index1 TO CA_ADDRESS_SK_index4 ;
+
+
语法格式
+
重命名表索引的名称。
ALTER INDEX [ IF EXISTS ] index_name
+ RENAME TO new_name;
+
+
修改表索引的所属空间。
ALTER INDEX [ IF EXISTS ] index_name
+ SET TABLESPACE tablespace_name;
+
+
修改表索引的存储参数。
ALTER INDEX [ IF EXISTS ] index_name
+ SET ( {storage_parameter = value} [, ... ] );
+
+
重置表索引的存储参数。
ALTER INDEX [ IF EXISTS ] index_name
+ RESET ( storage_parameter [, ... ] ) ;
+
+
设置表索引或索引分区不可用。
ALTER INDEX [ IF EXISTS ] index_name
+ [ MODIFY PARTITION index_partition_name ] UNUSABLE;
+
列存表不支持该语法。
+
+
+
重建表索引或索引分区。
ALTER INDEX index_name
+ REBUILD [ PARTITION index_partition_name ];
+
+
重命名索引分区。
ALTER INDEX [ IF EXISTS ] index_name
+ RENAME PARTITION index_partition_name TO new_index_partition_name;
+
+
修改索引分区的所属表空间。
ALTER INDEX [ IF EXISTS ] index_name
+ MOVE PARTITION index_partition_name TABLESPACE new_tablespace;
+
+
+
参数说明
+
+
index_name
+
要修改的索引名。
+
+
new_name
+
新的索引名。
+
取值范围：字符串，且符合标识符命名规范。
+
+
tablespace_name
+
表空间的名称。
+
取值范围：已存在的表空间。
+
+
storage_parameter
+
索引方法特定的参数名。
+
+
value
+
索引方法特定的存储参数的新值。根据参数的不同，这可能是一个数字或单词。
+
+
new_index_partition_name
+
新索引分区名。
+
+
index_partition_name
+
索引分区名。
+
+
new_tablespace
+
新表空间。
+
]]>
+
+
+
功能描述
+
ALTER LARGE OBJECT用于更改一个large object的定义。它的唯一的功能是分配一个新的所有者。
+
+
注意事项
+
使用ALTER LARGE OBJECT必须是系统管理员或者是其所有者。
+
+
语法格式
+
ALTER LARGE OBJECT large_object_oid
+ OWNER TO new_owner;
+
+
参数说明
+
+
large_object_oid
+
要被变large object的OID 。
+
取值范围：已存在的大对象名。
+
+
OWNER TO new_owner
+
large object新的所有者。
+
取值范围：已存在的用户名/角色名。
+
]]>
+
+
+
功能描述
+
修改角色属性。
+
+
示例
+
--修改角色manager的密码为abcd@123。
+postgres=# ALTER ROLE manager IDENTIFIED BY ' abcd@123 ' REPLACE ' Bigdata@123 ' ;
+
+--修改角色manager为系统管理员。
+postgres=# ALTER ROLE manager SYSADMIN ;
+
--设置当前会话的字符编码为UTF8。
+postgres=# ALTER SESSION SET NAMES ' UTF8 ' ;
+
+--设置当前模式。
+postgres=# ALTER SESSION SET CURRENT_SCHEMA TO tpcds ;
+
+--设置XML OPTION为DOCUMENT。
+postgres=# ALTER SESSION SET XML OPTION DOCUMENT ;
+
+--创建角色joe，并设置会话的角色为joe。
+postgres=# CREATE ROLE joe WITH PASSWORD ' Bigdata@123 ' ;
+postgres=# ALTER SESSION SET SESSION AUTHORIZATION joe PASSWORD ' Bigdata@123 ' ;
+
+--切换到默认用户。
+postgres=> ALTER SESSION SET SESSION AUTHORIZATION default;
+
+
语法格式
+
设置会话的事务参数。
ALTER SESSION SET [ SESSION CHARACTERISTICS AS ] TRANSACTION
+ { ISOLATION LEVEL { READ COMMITTED } | { READ ONLY | READ WRITE } } [, ...] ;
+
设置会话的其他运行时参数。
ALTER SESSION SET
+ {{config_parameter { { TO | = } { value | DEFAULT }
+ | FROM CURRENT }}
+ | TIME ZONE time_zone
+ | CURRENT_SCHEMA schema
+ | NAMES encoding_name
+ | ROLE role_name PASSWORD 'password'
+ | SESSION AUTHORIZATION { role_name PASSWORD 'password' | DEFAULT }
+ | XML OPTION { DOCUMENT | CONTENT }
+ } ;
--把表空间ds_location1重命名为ds_location3。
+postgres=# ALTER TABLESPACE ds_location1 RENAME TO ds_location3 ;
+
+--改变表空间ds_location2的所有者。
+postgres=# ALTER TABLESPACE ds_location2 OWNER TO jay ;
+
+
语法格式
+
重命名表空间的语法。
ALTER TABLESPACE tablespace_name
+ RENAME TO new_tablespace_name;
+
设置表空间所有者的语法。
ALTER TABLESPACE tablespace_name
+ OWNER TO new_owner;
+
设置表空间属性的语法。
ALTER TABLESPACE tablespace_name
+ SET ( {tablespace_option = value} [, ... ] );
ALTER MAPPING REPLACE ... WITH ... 与ALTER MAPPING FOR ... REPLACE ... WITH ...选项会直接使用new_dictionary替换old_dictionary。需要注意的是，只有pg_ts_config_map系统表中存在maptokentype与old_dictionary对应关系的元组时，才能更新成功，否则不会成功，也不会有任何提示信息返回。
+
DROP MAPPING FOR选项会删除当前文本搜索配置中指定的字串类型映射。 如果没有指定IF EXISTS选项，当DROP MAPPING FOR选项指定的字串类型映射在文本搜索配置中不存在时，数据库会报错。
+
+
注意事项
+
当一个搜索配置已经被引用（如被用来创建索引），则不允许用户修改此文本搜索配置。
要使用ALTER TEXT SEARCH CONFIGURATION，用户必须是配置的所有者。
+
+
示例
+
--增加文本搜索配置字串类型映射语法。
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ADD MAPPING FOR word WITH simple , english_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+--增加文本搜索配置字串类型映射语法。
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ADD MAPPING FOR email WITH english_stem , french_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+--增加文本搜索配置字串类型映射语法。
+postgres=# ALTER TEXT SEARCH CONFIGURATION english_1 ALTER MAPPING REPLACE french_stem with german_stem ;
+ALTER TEXT SEARCH CONFIGURATION
+
+
语法格式
+
增加文本搜索配置字串类型映射语法
+
ALTER TEXT SEARCH CONFIGURATION name
+ ADD MAPPING FOR token_type [, ... ] WITH dictionary_name [, ... ];
+
修改文本搜索配置字典语法
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING FOR token_type [, ... ] REPLACE old_dictionary WITH new_dictionary;
+
修改文本搜索配置字串类型语法
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING FOR token_type [, ... ] WITH dictionary_name [, ... ];
+
更改文本搜索配置字典语法
+
ALTER TEXT SEARCH CONFIGURATION name
+ ALTER MAPPING REPLACE old_dictionary WITH new_dictionary;
+
删除文本搜索配置字串类型映射语法
+
ALTER TEXT SEARCH CONFIGURATION name
+ DROP MAPPING [ IF EXISTS ] FOR token_type [, ... ];
+
重命名文本搜索配置所有者语法
+
ALTER TEXT SEARCH CONFIGURATION name OWNER TO new_owner;
+
重命名文本搜索配置名称语法
+
ALTER TEXT SEARCH CONFIGURATION name RENAME TO new_name;
+
重命名文本搜索配置命名空间语法
+
ALTER TEXT SEARCH CONFIGURATION name SET SCHEMA new_schema;
+
修改文本搜索配置属性语法
+
ALTER TEXT SEARCH CONFIGURATION name SET ( { configuration_option = value } [, ...] );
+
重置文本搜索配置属性语法
+
ALTER TEXT SEARCH CONFIGURATION name RESET ( {configuration_option} [, ...] );
--修改触发器
+postgres=# ALTER TRIGGER delete_trigger ON test_trigger_src_tbl RENAME TO delete_trigger_renamed ;
+
+--禁用insert_trigger触发器
+postgres=# ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER insert_trigger ;
+
+--禁用当前表上所有触发器
+postgres=# ALTER TABLE test_trigger_src_tbl DISABLE TRIGGER ALL ;
+
+
语法格式
+
ALTER TRIGGER trigger_name ON table_name RENAME TO new_name;
+
+
参数说明
+
+
trigger_name
+
要修改的触发器名称。
+
取值范围：已存在的触发器。
+
+
table_name
+
要修改的触发器所在的表名称。
+
取值范围：已存在的含触发器的表。
+
+
new_name
+
修改后的新名称。
+
取值范围：符合标识符命名规范的字符串，最大长度不超过63个字符，且不能与所在表上其他触发器同名。
+
]]>
+
+
+
功能描述
+
修改一个类型的定义。
+
+
示例
+
--重命名数据类型。
+postgres=# ALTER TYPE compfoo RENAME TO compfoo1 ;
+
+--要改变一个用户定义类型compfoo1的所有者为usr1。
+postgres=# CREATE USER usr1 PASSWORD ' Bigdata@123 ' ;
+postgres=# ALTER TYPE compfoo1 OWNER TO usr1 ;
+
+--把用户定义类型compfoo1的模式改变为usr1。
+postgres=# ALTER TYPE compfoo1 SET SCHEMA usr1 ;
+
+--给一个数据类型增加一个新的属性。
+postgres=# ALTER TYPE usr1.compfoo1 ADD ATTRIBUTE f3 int;
+
+--添加一个标签值。
+postgres=# ALTER TYPE bugstatus ADD VALUE IF NOT EXISTS ' regress ' BEFORE ' closed ' ;
+
+--重命名一个标签值。
+postgres=# ALTER TYPE bugstatus RENAME VALUE ' create ' TO ' new ' ;
+
+
语法格式
+
修改类型
ALTER TYPE name action [, ... ]
+ALTER TYPE name OWNER TO { new_owner | CURRENT_USER | SESSION_USER }
+ALTER TYPE name RENAME ATTRIBUTE attribute_name TO new_attribute_name [ CASCADE | RESTRICT ]
+ALTER TYPE name RENAME TO new_name
+ALTER TYPE name SET SCHEMA new_schema
+ALTER TYPE name ADD VALUE [ IF NOT EXISTS ] new_enum_value [ { BEFORE | AFTER } neighbor_enum_value ]
+ALTER TYPE name RENAME VALUE existing_enum_value TO new_enum_value
+
+where action is one of:
+ ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
+ DROP ATTRIBUTE [ IF EXISTS ] attribute_name [ CASCADE | RESTRICT ]
+ ALTER ATTRIBUTE attribute_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
+
给复合类型增加新的属性。
ALTER TYPE name ADD ATTRIBUTE attribute_name data_type [ COLLATE collation ] [ CASCADE | RESTRICT ]
--将用户jim的登录密码由Bigdata@123修改为Abcd@123。
+postgres=# ALTER USER jim IDENTIFIED BY ' Abcd@123 ' REPLACE ' Bigdata@123 ' ;
+
+--为用户jim追加CREATEROLE权限。
+postgres=# ALTER USER jim CREATEROLE ;
+
+--将enable_seqscan的值设置为on， 设置成功后，在下一会话中生效。
+postgres=# ALTER USER jim SET enable_seqscan TO on ;
+
+--重置jim的enable_seqscan参数。
+postgres=# ALTER USER jim RESET enable_seqscan ;
+
+--锁定jim帐户。
+postgres=# ALTER USER jim ACCOUNT LOCK ;
+
--修改视图名称。
+postgres=# ALTER VIEW tpcds.customer_details_view_v1 RENAME TO customer_details_view_v2 ;
+
+--修改视图所属schema。
+postgres=# ALTER VIEW tpcds.customer_details_view_v2 SET schema public ;
+
+
语法格式
+
设置视图列的默认值。
ALTER VIEW [ IF EXISTS ] view_name
+ ALTER [ COLUMN ] column_name SET DEFAULT expression;
+
取消列视图列的默认值。
ALTER VIEW [ IF EXISTS ] view_name
+ ALTER [ COLUMN ] column_name DROP DEFAULT;
+
修改视图的所有者。
ALTER VIEW [ IF EXISTS ] view_name
+ OWNER TO new_owner;
+
重命名视图。
ALTER VIEW [ IF EXISTS ] view_name
+ RENAME TO new_name;
+
设置视图的所属模式。
ALTER VIEW [ IF EXISTS ] view_name
+ SET SCHEMA new_schema;
+
设置视图的选项。
ALTER VIEW [ IF EXISTS ] view_name
+ SET ( { view_option_name [ = view_option_value ] } [, ... ] );
+
重置视图的选项。
ALTER VIEW [ IF EXISTS ] view_name
+ RESET ( view_option_name [, ... ] );
COMMIT PREPARED transaction_id ;
+COMMIT PREPARED transaction_id WITH CSN;
+
+
参数说明
+
+
transaction_id
+
待提交事务的标识符。它不能和任何当前预备事务已经使用了的标识符同名。
+
+
CSN(commit sequence number)
+
待提交事务的序列号。它是一个64位递增无符号数。
+
]]>
+
+
+
功能描述
+
通过COPY命令实现在表和文件之间拷贝数据。
+
COPY FROM从一个文件拷贝数据到一个表，COPY TO把一个表的数据拷贝到一个文件。
+
+
注意事项
+
执行COPY FROM FILENAME或COPY TO FILENAME语句需要SYSADMIN权限，但默认禁止SYSADMIN用户对数据库配置文件，密钥文件，证书文件和审计日志执行COPY FROM FILENAME或COPY TO FILENAME，以防止SYSADMIN用户越权查看或修改敏感文件。放开这一权限需要通过更改enable_copy_server_files的设定来完成。
-- 为用户role1创建一个同名schema，子命令创建的表films和winners的拥有者为role1。
+postgres=# CREATE SCHEMA AUTHORIZATION role1
+CREATE TABLE films ( title text , release date , awards text[] )
+CREATE VIEW winners AS
+SELECT title , release FROM films WHERE awards IS NOT NULL ;
+
该情形下，分区键支持的数据类型为：SMALLINT、INTEGER、BIGINT、DECIMAL、NUMERIC、REAL、DOUBLE PRECISION、CHARACTER VARYING(n)、VARCHAR(n)、CHARACTER(n)、CHAR(n)、CHARACTER、CHAR、TEXT、NVARCHAR2、NAME、TIMESTAMP[(p)] [WITHOUT TIME ZONE]、TIMESTAMP[(p)] [WITH TIME ZONE]、DATE。
+
（2）对于从句是START END的语法格式：
+
对于从句是START END的语法格式，范围分区策略的分区键仅支持1列。
+
+
该情形下，分区键支持的数据类型为：SMALLINT、INTEGER、BIGINT、DECIMAL、NUMERIC、REAL、DOUBLE PRECISION、TIMESTAMP[(p)] [WITHOUT TIME ZONE]、TIMESTAMP[(p)] [WITH TIME ZONE]、DATE。
+
+
PARTITION partition_name VALUES LESS THAN ( { partition_value | MAXVALUE } )
--创建用户jim，登录密码为Bigdata@123。
+postgres=# CREATE USER jim PASSWORD ' Bigdata@123 ' ;
+
+--下面语句与上面的等价。
+postgres=# CREATE USER kim IDENTIFIED BY ' Bigdata@123 ' ;
+
+--如果创建有“创建数据库”权限的用户，则需要加CREATEDB关键字。
+postgres=# CREATE USER dim CREATEDB PASSWORD ' Bigdata@123 ' ;
+
+
语法格式
+
CREATE USER user_name [ [ WITH ] option [ ... ] ] [ ENCRYPTED | UNENCRYPTED ] { PASSWORD | IDENTIFIED BY } { 'password' | DISABLE };
--授予用户webuser对模式tpcds下视图的所有操作权限。
+postgres=# DO $$DECLARE r record ;
+BEGIN
+FOR r IN SELECT c.relname table_name , n.nspname table_schema FROM pg_class c , pg_namespace n
+WHERE c.relnamespace = n.oid AND n.nspname = ' tpcds ' AND relkind IN ( ' r ' , ' v ' )
+LOOP
+EXECUTE ' GRANT ALL ON ' || quote_ident ( r.table_schema ) || ' . ' || quote_ident ( r.table_name ) || ' TO webuser ' ;
+END LOOP ;
+END$$ ;
+
postgres=# CREATE USER joe PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT ALL PRIVILEGES TO joe ;
+授权成功后，用户joe会拥有sysadmin的所有权限。
+示例：将对象权限授权给用户或者角色。
+撤销joe用户的sysadmin权限，然后将模式tpcds的使用权限和表tpcds.reason的所有权限授权给用户joe。postgres=# REVOKE ALL PRIVILEGES FROM joe ;
+postgres=# GRANT USAGE ON SCHEMA tpcds TO joe ;
+postgres=# GRANT ALL PRIVILEGES ON tpcds.reason TO joe ;
+授权成功后，joe用户就拥有了tpcds.reason表的所有权限，包括增删改查等权限。
+将tpcds.reason表中r_reason_sk、r_reason_id、r_reason_desc列的查询权限，r_reason_desc的更新权限授权给joe。postgres=# GRANT select ( r_reason_sk , r_reason_id , r_reason_desc ) , update ( r_reason_desc ) ON tpcds.reason TO joe ;
+授权成功后，用户joe对tpcds.reason表中r_reason_sk，r_reason_id的查询权限会立即生效。如果joe用户需要拥有将这些权限授权给其他用户的权限，可以通过以下语法对joe用户进行授权。
+postgres=# GRANT select ( r_reason_sk , r_reason_id ) ON tpcds.reason TO joe WITH GRANT OPTION ;
+将数据库postgres的连接权限授权给用户joe，并给予其在postgres中创建schema的权限，而且允许joe将此权限授权给其他用户。
+postgres=# GRANT create , connect on database postgres TO joe WITH GRANT OPTION ;
+创建角色tpcds_manager，将模式tpcds的访问权限授权给角色tpcds_manager，并授予该角色在tpcds下创建对象的权限，不允许该角色中的用户将权限授权给其他人。
+postgres=# CREATE ROLE tpcds_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT USAGE , CREATE ON SCHEMA tpcds TO tpcds_manager ;
+将表空间tpcds_tbspc的所有权限授权给用户joe，但用户joe无法将权限继续授予其他用户。
+postgres=# CREATE TABLESPACE tpcds_tbspc RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+postgres=# GRANT ALL ON TABLESPACE tpcds_tbspc TO joe ;
+示例：将用户或者角色的权限授权给其他用户或角色。
+创建角色manager，将joe的权限授权给manager，并允许该角色将权限授权给其他人。postgres=# CREATE ROLE manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT joe TO manager WITH ADMIN OPTION ;
+创建用户senior_manager，将用户manager的权限授权给该用户。postgres=# CREATE ROLE senior_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT manager TO senior_manager ;
+撤销权限，并清理用户。postgres=# REVOKE manager FROM joe ;
+postgres=# REVOKE senior_manager FROM manager ;
+postgres=# DROP USER manager ;
+示例：撤销上述授予的权限，并清理角色和用户。
+postgres=# REVOKE ALL PRIVILEGES ON tpcds.reason FROM joe ;
+postgres=# REVOKE ALL PRIVILEGES ON SCHEMA tpcds FROM joe ;
+postgres=# REVOKE ALL ON TABLESPACE tpcds_tbspc FROM joe ;
+postgres=# DROP TABLESPACE tpcds_tbspc ;
+postgres=# REVOKE USAGE , CREATE ON SCHEMA tpcds FROM tpcds_manager ;
+postgres=# DROP ROLE tpcds_manager ;
+postgres=# DROP ROLE senior_manager ;
+postgres=# DROP USER joe CASCADE ;
+
+
语法格式
+
将表或视图的访问权限赋予指定的用户或角色。
GRANT { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON { [ TABLE ] table_name [, ...]
+ | ALL TABLES IN SCHEMA schema_name [, ...] }
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
+
将表中字段的访问权限赋予指定的用户或角色。
GRANT { {{ SELECT | INSERT | UPDATE | REFERENCES } ( column_name [, ...] )} [, ...]
+ | ALL [ PRIVILEGES ] ( column_name [, ...] ) }
+ ON [ TABLE ] table_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将数据库的访问权限赋予指定的用户或角色。
GRANT { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON DATABASE database_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将域的访问权限赋予指定的用户或角色。
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON DOMAIN domain_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
本版本暂时不支持赋予域的访问权限。
+
+
将外部数据源的访问权限赋予给指定的用户或角色。
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON FOREIGN DATA WRAPPER fdw_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将外部服务器的访问权限赋予给指定的用户或角色。
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON FOREIGN SERVER server_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将函数的访问权限赋予给指定的用户或角色。
GRANT { EXECUTE | ALL [ PRIVILEGES ] }
+ ON { FUNCTION {function_name ( [ {[ argmode ] [ arg_name ] arg_type} [, ...] ] )} [, ...]
+ | ALL FUNCTIONS IN SCHEMA schema_name [, ...] }
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将过程语言的访问权限赋予给指定的用户或角色。
GRANT { USAGE | ALL [ PRIVILEGES ] }
+ ON LANGUAGE lang_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
将大对象的访问权限赋予指定的用户或角色。
GRANT { { SELECT | UPDATE } [, ...] | ALL [ PRIVILEGES ] }
+ ON LARGE OBJECT loid [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
+
本版本暂时不支持大对象。
+
+
将模式的访问权限赋予指定的用户或角色。
GRANT { { CREATE | USAGE } [, ...] | ALL [ PRIVILEGES ] }
+ ON SCHEMA schema_name [, ...]
+ TO { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ WITH GRANT OPTION ];
如果是INSERT ON DUPLICATE KEY UPDATE语句下，expression可以为VALUES(column_name)或EXCLUDED.column_name用来表示引用冲突行对应的column_name字段的值。需注意，其中VALUES(column_name)不支持嵌套在表达式中（例如VALUES(column_name)+1），但EXCLUDED不受此限制。
openGauss在为一个引用了表的命令自动请求锁时，尽可能选择最小限制的锁模式。如果用户需要一种更为严格的锁模式，可以使用LOCK命令。例如，一个应用是在Read Committed隔离级别上运行事务，并且它需要保证表中的数据在事务的运行过程中不被修改。为实现这个目的，则可以在查询之前对表使用SHARE锁模式进行锁定。这样将防止数据不被并发修改，从而保证后续的查询可以读到已提交的持久化的数据。因为SHARE锁模式与任何写操作需要的ROW EXCLUSIVE模式冲突，并且LOCK TABLE name IN SHARE MODE语句将等到所有当前持有ROW EXCLUSIVE模式锁的事务提交或回滚后才能执行。因此，一旦获得该锁，就不会存在未提交的写操作，并且其他操作也只能等到该锁释放之后才能开始。
RESET {configuration_parameter | CURRENT_SCHEMA | TIME ZONE | TRANSACTION ISOLATION LEVEL | SESSION AUTHORIZATION | ALL };
+
+
参数说明
+
+
configuration_parameter
+
运行时参数的名称。
+
取值范围：可以使用SHOW ALL命令查看运行时参数。
+
+
CURRENT_SCHEMA
+
当前模式
+
+
TIME ZONE
+
时区。
+
+
TRANSACTION ISOLATION LEVEL
+
事务的隔离级别。
+
+
SESSION AUTHORIZATION
+
当前会话的用户标识符。
+
+
ALL
+
所有运行时参数。
+
]]>
+
+
+
功能描述
+
REVOKE用于撤销一个或多个角色的权限。
+
+
注意事项
+
非对象所有者试图在对象上REVOKE权限，命令按照以下规则执行：
+
如果授权用户没有该对象上的权限，则命令立即失败。
如果授权用户有部分权限，则只撤销那些有授权选项的权限。
如果授权用户没有授权选项，REVOKE ALL PRIVILEGES形式将发出一个错误信息，而对于其他形式的命令而言，如果是命令中指定名称的权限没有相应的授权选项，该命令将发出一个警告。
不允许对表分区进行REVOKE操作，对分区表进行REVOKE操作会引起告警。
+
+
示例
+
postgres=# CREATE USER joe PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT ALL PRIVILEGES TO joe ;
+授权成功后，用户joe会拥有sysadmin的所有权限。
+示例：将对象权限授权给用户或者角色。
+撤销joe用户的sysadmin权限，然后将模式tpcds的使用权限和表tpcds.reason的所有权限授权给用户joe。postgres=# REVOKE ALL PRIVILEGES FROM joe ;
+postgres=# GRANT USAGE ON SCHEMA tpcds TO joe ;
+postgres=# GRANT ALL PRIVILEGES ON tpcds.reason TO joe ;
+授权成功后，joe用户就拥有了tpcds.reason表的所有权限，包括增删改查等权限。
+将tpcds.reason表中r_reason_sk、r_reason_id、r_reason_desc列的查询权限，r_reason_desc的更新权限授权给joe。postgres=# GRANT select ( r_reason_sk , r_reason_id , r_reason_desc ) , update ( r_reason_desc ) ON tpcds.reason TO joe ;
+授权成功后，用户joe对tpcds.reason表中r_reason_sk，r_reason_id的查询权限会立即生效。如果joe用户需要拥有将这些权限授权给其他用户的权限，可以通过以下语法对joe用户进行授权。
+postgres=# GRANT select ( r_reason_sk , r_reason_id ) ON tpcds.reason TO joe WITH GRANT OPTION ;
+将数据库postgres的连接权限授权给用户joe，并给予其在postgres中创建schema的权限，而且允许joe将此权限授权给其他用户。
+postgres=# GRANT create , connect on database postgres TO joe WITH GRANT OPTION ;
+创建角色tpcds_manager，将模式tpcds的访问权限授权给角色tpcds_manager，并授予该角色在tpcds下创建对象的权限，不允许该角色中的用户将权限授权给其他人。
+postgres=# CREATE ROLE tpcds_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT USAGE , CREATE ON SCHEMA tpcds TO tpcds_manager ;
+将表空间tpcds_tbspc的所有权限授权给用户joe，但用户joe无法将权限继续授予其他用户。
+postgres=# CREATE TABLESPACE tpcds_tbspc RELATIVE LOCATION ' tablespace/tablespace_1 ' ;
+postgres=# GRANT ALL ON TABLESPACE tpcds_tbspc TO joe ;
+示例：将用户或者角色的权限授权给其他用户或角色。
+创建角色manager，将joe的权限授权给manager，并允许该角色将权限授权给其他人。postgres=# CREATE ROLE manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT joe TO manager WITH ADMIN OPTION ;
+创建用户senior_manager，将用户manager的权限授权给该用户。postgres=# CREATE ROLE senior_manager PASSWORD ' Bigdata@123 ' ;
+postgres=# GRANT manager TO senior_manager ;
+撤销权限，并清理用户。postgres=# REVOKE manager FROM joe ;
+postgres=# REVOKE senior_manager FROM manager ;
+postgres=# DROP USER manager ;
+示例：撤销上述授予的权限，并清理角色和用户。
+postgres=# REVOKE ALL PRIVILEGES ON tpcds.reason FROM joe ;
+postgres=# REVOKE ALL PRIVILEGES ON SCHEMA tpcds FROM joe ;
+postgres=# REVOKE ALL ON TABLESPACE tpcds_tbspc FROM joe ;
+postgres=# DROP TABLESPACE tpcds_tbspc ;
+postgres=# REVOKE USAGE , CREATE ON SCHEMA tpcds FROM tpcds_manager ;
+postgres=# DROP ROLE tpcds_manager ;
+postgres=# DROP ROLE senior_manager ;
+postgres=# DROP USER joe CASCADE ;
+
+
语法格式
+
回收指定表和视图上权限。
REVOKE [ GRANT OPTION FOR ]
+ { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES }[, ...]
+ | ALL [ PRIVILEGES ] }
+ ON { [ TABLE ] table_name [, ...]
+ | ALL TABLES IN SCHEMA schema_name [, ...] }
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收表上指定字段权限。
REVOKE [ GRANT OPTION FOR ]
+ { {{ SELECT | INSERT | UPDATE | REFERENCES } ( column_name [, ...] )}[, ...]
+ | ALL [ PRIVILEGES ] ( column_name [, ...] ) }
+ ON [ TABLE ] table_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收指定数据库上权限。
REVOKE [ GRANT OPTION FOR ]
+ { { CREATE | CONNECT | TEMPORARY | TEMP } [, ...]
+ | ALL [ PRIVILEGES ] }
+ ON DATABASE database_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收指定函数上权限。
REVOKE [ GRANT OPTION FOR ]
+ { EXECUTE | ALL [ PRIVILEGES ] }
+ ON { FUNCTION {function_name ( [ {[ argmode ] [ arg_name ] arg_type} [, ...] ] )} [, ...]
+ | ALL FUNCTIONS IN SCHEMA schema_name [, ...] }
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收指定大对象上权限。
REVOKE [ GRANT OPTION FOR ]
+ { { SELECT | UPDATE } [, ...] | ALL [ PRIVILEGES ] }
+ ON LARGE OBJECT loid [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收指定模式上权限。
REVOKE [ GRANT OPTION FOR ]
+ { { CREATE | USAGE } [, ...] | ALL [ PRIVILEGES ] }
+ ON SCHEMA schema_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
回收指定表空间上权限。
REVOKE [ GRANT OPTION FOR ]
+ { CREATE | ALL [ PRIVILEGES ] }
+ ON TABLESPACE tablespace_name [, ...]
+ FROM { [ GROUP ] role_name | PUBLIC } [, ...]
+ [ CASCADE | RESTRICT ];
+
按角色回收角色上的权限。
REVOKE [ ADMIN OPTION FOR ]
+ role_name [, ...] FROM role_name [, ...]
+ [ CASCADE | RESTRICT ];
+
回收角色上的sysadmin权限。
REVOKE ALL { PRIVILEGES | PRIVILEGE } FROM role_name;
ROLLBACK TO SAVEPOINT用于回滚到一个保存点，隐含地删除所有在该保存点之后建立的保存点。
+
回滚所有指定保存点建立之后执行的命令。保存点仍然有效，并且需要时可以再次回滚到该点。
+
+
注意事项
+
不能回滚到一个未定义的保存点，语法上会报错。
在保存点方面，游标有一些非事务性的行为。任何在保存点里打开的游标都会在回滚掉这个保存点之后关闭。如果一个前面打开了的游标在保存点里面，并且游标被一个FETCH命令影响，而这个保存点稍后回滚了，那么这个游标的位置仍然在FETCH让它指向的位置(也就是FETCH不会被回滚)。关闭一个游标的行为也不会被回滚给撤消掉。如果一个游标的操作导致事务回滚，那么这个游标就会置于不可执行状态，所以，尽管一个事务可以用ROLLBACK TO SAVEPOINT重新恢复，但是游标不能再使用了。
使用ROLLBACK TO SAVEPOINT回滚到一个保存点。使用RELEASE SAVEPOINT删除一个保存点，但是保留该保存点建立后执行的命令的效果。
SQL标准要求，使用savepoint建立一个同名保存点时，需要自动删除前面那个同名保存点。在openGauss数据库里，我们将保留旧的保存点，但是在回滚或者释放的时候，只使用最近的那个。释放了新的保存点将导致旧的再次成为ROLLBACK TO SAVEPOINT和RELEASE SAVEPOINT可以访问的保存点。除此之外，SAVEPOINT是完全符合SQL标准的。
');
+ divGoBack.append(img1);
+ $(".grammar-item-one").append(divGoBack);
+ }
+}
+
+function readWorkbookFromRemoteFile(callback) {
+ var xhr = new XMLHttpRequest();
+ xhr.open('get', url, true);
+ xhr.responseType = 'arraybuffer';
+ xhr.onload = function(e) {
+ if (xhr.status == 200) {
+ var data = new Uint8Array(xhr.response)
+ var workbook = XLSX.read(data, { type: 'array' });
+ if (callback) callback(workbook);
+ }
+ };
+ xhr.send();
+}
+$(function() {
+ $("#keywordInfo").scrollBar({
+ width: 252
+ });
+ setTimeout(function() { //用于在指定的毫秒数后调用函数或计算表达式
+ myCallDBAssistantLoad('');
+ }, 1000);
+ $('body').contextmenu(function(event) {
+ //hideKeyWordList();
+ if (document.selection) {
+ oTextSelection = document.selection.createRange().text;
+ } else {
+ oTextSelection = window.getSelection().toString();
+ }
+ //var event = event || window.event;
+ var leftX = event.pageX;
+ var topY = event.pageY;
+
+ if (oTextSelection != "" && rightMenu == "") {
+ var bodyW = $('body').width();
+ if (bodyW <= leftX + 130) {
+ leftX = bodyW - 130;
+ }
+ rightMenu = $('');
+ var span1 = $('
