diff --git "a/content/zh/post/liuxu/openGauss\345\206\205\345\255\230\344\274\230\345\214\226\350\241\250\346\234\200\344\275\263\345\256\236\350\267\265.md" "b/content/zh/post/liuxu/openGauss\345\206\205\345\255\230\344\274\230\345\214\226\350\241\250\346\234\200\344\275\263\345\256\236\350\267\265.md" deleted file mode 100644 index ee685188a6f7f814301705d5276754216b84db70..0000000000000000000000000000000000000000 --- "a/content/zh/post/liuxu/openGauss\345\206\205\345\255\230\344\274\230\345\214\226\350\241\250\346\234\200\344\275\263\345\256\236\350\267\265.md" +++ /dev/null @@ -1,811 +0,0 @@ -+++ - -title = "openGauss内存优化表最佳实践" - -date = "2020-12-17" - -tags = ["openGauss最佳实践"] - -archives = "2020-12" - -author = "刘旭" - -summary = "openGauss内存优化表最佳实践" - -img = "/zh/post/liuxu/title/img122.png" - -times = "18:30" - -+++ - -# openGauss内存优化表最佳实践 - -## 适用版本 - -openGauss 1.0.1 build和更高版本。 - -## 用途 - -概述MOT（内存优化表）的特性，如何在openGauss数据库中创建和使用MOT。 - -## MOT概述 - -openGauss引入了MOT存储引擎，它是一种事务性行存储，针对多核和大内存服务器进行了优化。MOT是openGauss数据库最先进的生产级特性（Beta版本），它为事务性工作负载提供更高的性能。MOT完全支持ACID特性，并包括严格的持久性和高可用性支持。企业可以在关键任务、性能敏感的在线事务处理（OLTP）中使用MOT，以实现高性能、高吞吐、可预测低延迟以及多核服务器的高利用率。 - -![](../figures/22.png) - -**使用MOT** - -1. 授予用户权限 - - ``` - postgres=# select usename,usesysid from pg_user; - usename | usesysid - ---------+---------- - omm | 10 - (1 row) - 要使omm用户能够创建和访问MOT（DDL、DML、SELECT），以下语句只执行一次 - GRANT USAGE ON FOREIGN SERVER mot_server TO omm; - ``` - -2. 创建/删除MOT - - 检查参数 - - ``` - postgres=# show enable_incremental_checkpoint; - enable_incremental_checkpoint - ------------------------------ - on - ``` - - 如果enable\_incremental\_checkpoint显示为on，则修改为off，并重启数据库 - - ``` - alter system set enable_incremental_checkpoint='off'; - gs_om -t stop - gs_om -t start - postgres=# show enable_incremental_checkpoint; - enable_incremental_checkpoint - ------------------------------- - off - (1 row) - ``` - - 创建MOT表mot\_1，并创建索引 - - ``` - postgres=# create FOREIGN table mot_1 - postgres-# (o_w_id integer not null, - postgres(# o_d_id integer not null, - postgres(# o_id integer not null, - postgres(# o_c_id integer not null, - postgres(# o_carrier_id integer, - postgres(# o_ol_cnt integer, - postgres(# o_all_local integer, - postgres(# o_entry_d timestamp, - postgres(# primary key (o_w_id, o_d_id, o_id)); - NOTICE: CREATE FOREIGN TABLE / PRIMARY KEY will create constraint "mot_1_pkey" for foreign table "mot_1" - CREATE FOREIGN TABLE - - postgres=# create index mot_1_index1 on mot_1(o_w_id, o_d_id, o_c_id, o_id) ; - CREATE INDEX - ``` - - 插入200000随机数据。 - - ``` - postgres=# insert into mot_1 select ceil(random()*(10000-1)+1),ceil(random()*(10000-10)+10),ceil(random()*(10000-100)+100),ceil(random()*(10000-1)+1),ceil(random()*(1000-1)+1),ceil(random()*(1000-1)+1),ceil(random()*(1000-1)+1),sysdate - postgres-# FROM generate_series(1,200000); - INSERT 0 200000 - Time: 4202.304 ms - ``` - - 通过执行计划查看MOT表 - - 说明：执行计划中-\>Memory Engine表示从内存中获取数据 - - ``` - postgres=# explain select * from mot_1; - QUERY PLAN - ------------------------------------------------------------------- - Foreign Scan on mot_1 (cost=0.10..20000.00 rows=200000 width=36) - -> Memory Engine returned rows: 0 - (2 rows) - ``` - - select所有列数据不包含where条件 - - ``` - postgres=# select * from mot_1 limit 5; - o_w_id | o_d_id | o_id | o_c_id | o_carrier_id | o_ol_cnt | o_all_local | o_entry_d - --------+--------+------+--------+--------------+----------+-------------+--------------------- - 2 | 291 | 8858 | 4033 | 274 | 681 | 655 | 2020-11-26 11:03:34 - 2 | 962 | 7972 | 1996 | 684 | 646 | 399 | 2020-11-26 11:03:34 - 2 | 1750 | 1415 | 1597 | 758 | 508 | 163 | 2020-11-26 11:03:34 - 2 | 2315 | 2449 | 1049 | 418 | 585 | 61 | 2020-11-26 11:03:34 - 2 | 2444 | 4531 | 274 | 461 | 120 | 503 | 2020-11-26 11:03:34 - (5 rows) - ``` - - select所有列数据包含索引列 - - _说明：内存表可以通过索引访问数据__ Index Scan on: mot\_1\_pkey1_ - - ``` - postgres=# explain select * from mot_1 where o_w_id = 2 limit 4; - QUERY PLAN - -------------------------------------------------------------------- - Limit (cost=0.00..4.00 rows=4 width=36) - -> Foreign Scan on mot_1 (cost=0.00..211.00 rows=211 width=36) - -> Memory Engine returned rows: 0 - -> Index Scan on: mot_1_pkey1 - Index Cond: (mot_1.o_w_id = 2) - - postgres=# select * from mot_1 where o_w_id = 2 limit 4; - o_w_id | o_d_id | o_id | o_c_id | o_carrier_id | o_ol_cnt | o_all_local | o_entry_d - --------+--------+------+--------+--------------+----------+-------------+--------------------- - 2 | 291 | 8858 | 4033 | 274 | 681 | 655 | 2020-11-26 11:03:34 - 2 | 962 | 7972 | 1996 | 684 | 646 | 399 | 2020-11-26 11:03:34 - 2 | 1750 | 1415 | 1597 | 758 | 508 | 163 | 2020-11-26 11:03:34 - 2 | 2315 | 2449 | 1049 | 418 | 585 | 61 | 2020-11-26 11:03:34 - ``` - - 两张表关联查询 - - 新建MOT表mot\_2 - - ``` - postgres=# create FOREIGN table mot_2 - postgres-# (o_w_id integer not null, - postgres(# o_d_id integer not null, - postgres(# o_id integer not null); - CREATE FOREIGN TABLE - Time: 3.359 ms - ``` - - 查看执行计划（mot\_2表无索引），通过Hash Join的方式做表关联 - - ``` - postgres=# explain select a.o_w_id,b.o_id from mot_2 a,mot_1 b where a.o_w_id = b.o_w_id; - QUERY PLAN - -------------------------------------------------------------------------------- - Hash Join (cost=11250.10..1156750.00 rows=500 width=8) - Hash Cond: (b.o_w_id = a.o_w_id) - -> Foreign Scan on mot_1 b (cost=0.10..20000.00 rows=200000 width=8) - -> Memory Engine returned rows: 0 - -> Hash (cost=10000.00..10000.00 rows=100000 width=4) - -> Foreign Scan on mot_2 a (cost=0.10..10000.00 rows=100000 width=4) - -> Memory Engine returned rows: 0 - (7 rows) - ``` - - 查看执行计划（mot\_2有单列索引），通过访问索引Nested Loop的方式访问数据 - - ``` - postgres=# create index mot_2_index1 on mot_1(o_w_id) ; - CREATE INDEX - Time: 437.916 ms - - postgres=# explain select a.o_w_id,b.o_id from mot_2 a,mot_1 b where a.o_w_id = b.o_w_id; - QUERY PLAN - -------------------------------------------------------------------------- - Nested Loop (cost=0.10..111000.00 rows=500 width=8) - -> Foreign Scan on mot_2 a (cost=0.10..10000.00 rows=100000 width=4) - -> Memory Engine returned rows: 0 - -> Foreign Scan on mot_1 b (cost=0.00..1.00 rows=1 width=8) - Filter: (a.o_w_id = o_w_id) - -> Memory Engine returned rows: 0 - -> Index Scan on: mot_2_index1 - Index Cond: (b.o_w_id = $0) - (8 rows) - ``` - - update单表非索引字段 - - 将update o\_w\_id=2的非索引字段 - - ``` - postgres=# select count(*) from mot_1 where o_w_id=2; - count - ------- - 21 - (1 row) - ``` - - 已更新21条 - - ``` - postgres=# update mot_1 set o_all_local = 2020,o_ol_cnt=9090 where o_w_id=2; - UPDATE 21 - Time: 0.672 ms - ``` - - update单表索引字段 - - 将update o\_w\_id=2的索引字段 - - ``` - postgres=# select count(*) from mot_1 where o_w_id=2; - count - ------- - 21 - (1 row) - ``` - - 无法更新 - - ``` - postgres=# update mot_1 set o_w_id=2020 where o_w_id=2; - ERROR: Update of indexed column is not supported for memory table - Time: 0.302 ms - ``` - - update含有子查询 - - mot\_2 o\_w\_id = 2的数据\(2000条\) - - ``` - postgres=# select count(o_w_id) from mot_2; - count - ------- - 2000 - (1 row) - ``` - - 更新mot\_1中o\_w\_id in（select o\_w\_id from mot\_2 where o\_w\_id = 2）的数据 - - ``` - postgres=# update mot_1 set o_all_local = 2020,o_ol_cnt=9090 where o_w_id in (select o_w_id from mot_2 where o_w_id = 2); - UPDATE 21 - Time: 13.429 ms - ``` - - 查询mot\_1中o\_all\_local = 2020 and o\_ol\_cnt=9090的数据 - - ``` - postgres=# Select * from mot_1 where o_all_local = 2020 and o_ol_cnt=9090; - o_w_id | o_d_id | o_id | o_c_id | o_carrier_id | o_ol_cnt | o_all_local | o_entry_d - --------+--------+------+--------+--------------+----------+-------------+--------------------- - 2 | 291 | 8858 | 4033 | 274 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 962 | 7972 | 1996 | 684 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 1750 | 1415 | 1597 | 758 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 2315 | 2449 | 1049 | 418 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 2444 | 4531 | 274 | 461 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 2761 | 2627 | 7693 | 169 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 3300 | 3947 | 167 | 997 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 3921 | 424 | 4765 | 557 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 4216 | 2304 | 4065 | 829 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 5401 | 8904 | 8009 | 856 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 5416 | 9478 | 2939 | 959 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 5696 | 9749 | 7707 | 330 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 5935 | 2938 | 324 | 210 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 6680 | 4998 | 5906 | 439 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 6983 | 2343 | 18 | 87 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 7274 | 3141 | 6374 | 941 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 7292 | 6505 | 9174 | 989 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 7740 | 3702 | 8976 | 958 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 7828 | 7520 | 1161 | 387 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 8223 | 9573 | 7540 | 622 | 9090 | 2020 | 2020-11-26 11:03:34 - 2 | 8327 | 4427 | 8846 | 519 | 9090 | 2020 | 2020-11-26 11:03:34 - (21 rows) - - Time: 110.945 ms - ``` - - delete单表（删除o\_w\_id = 3的所有数据） - - ``` - postgres=# select count(*) from mot_1 where o_w_id = 3; - count - ------- - 26 - (1 row) - - postgres=# delete from mot_1 where o_w_id = 3; - DELETE 26 - postgres=# commit; - COMMIT - postgres=# select count(*) from mot_1 where o_w_id = 3; - count - ------- - 0 - (1 row) - ``` - - delete带有子查询（删除在mot\_2表中 o\_w\_id = 5的mot\_1表的所有数据） - - ``` - postgres=# delete from mot_1 where o_w_id in (select o_w_id from mot_2 where o_w_id = 5 ); - DELETE 15 - postgres=# commit; - COMMIT - ``` - - truncate操作（truncate mot\_2表） - - ``` - postgres=# truncate table mot_2; - TRUNCATE TABLE - ``` - - 事务的commit和rollback - - truncate（commit） - - 结论： - - 1、truncate操作可以rollback。 - - 2、当会话1执行truncate之后（没有commit），会话2对该表执行select操作处于等待状态。 - - 3、会话1执行commit或者rollback之后，其它会话可以正常dml操作。 - - 会话1 - - ``` - postgres=# truncate table mot_2; - TRUNCATE TABLE - postgres=# select count(*) from mot_2; - count - ------- - 0 - (1 row) - postgres=# commit; - COMMIT - postgres=# - ``` - - 会话2 - - ``` - postgres=# select * from mot_2; - 等待状态… - 等待会话1 commit之后 - postgres=# select * from mot_2; - o_w_id | o_d_id | o_id - --------+--------+------ - (0 rows) - ``` - - truncate（rollback） - - insert mot\_2表 2000条数据 - - ``` - postgres=# insert into mot_2 select ceil(random()*(10000-1)+1),ceil(random()*(10000-10)+10),ceil(random()*(10000-100)+100) FROM generate_series(1,2000); - - INSERT 0 2000 - postgres=# postgres=# commit; - COMMIT - postgres=# select count(*) from mot_2; - count - ------- - 2000 - (1 row) - ``` - - ``` - postgres=# truncate table mot_2; - TRUNCATE TABLE - postgres=# select count(*) from mot_2; - count - ------- - 0 - (1 row) - postgres=# rollback; - ROLLBACK - postgres=# select count(*) from mot_2; - count - ------- - 2000 - (1 row) - ``` - - update\(commit和rollback\) - - 结论： - - 1、会话1做update操作（commit之前），会话2依然可以对同一批数据做出不同的更改，不会出现悲观锁等待。 - - 2、最终的数据以最先commit的操作为准。 - - 会话1 - - ``` - select * from mot_2 where o_w_id = 5573; - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 7777 - 5573 | 2162 | 7777 - (2 rows) - ``` - - 会话2 - - ``` - select * from mot_2 where o_w_id = 5573; - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 7777 - 5573 | 2162 | 7777 - (2 rows) - ``` - - 会话1 - - ``` - postgres=# update mot_2 set o_id = 9999 where o_w_id = 5573; - UPDATE 2 - ``` - - 会话2 - - ``` - postgres=# update mot_2 set o_id = 3333 where o_w_id = 5573; - UPDATE 2 - ``` - - --在会话1没有commit或者rolllback时，会话2可以修改同一批数据，修改成功 - - 会话1 --看到的是当前会话已修改o\_id=9999的数据 - - ``` - select * from mot_2 where o_w_id = 5573; - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 9999 - 5573 | 2162 | 9999 - (2 rows) - ``` - - 会话2 --看到的是当前会话已修改o\_id=3333的数据 - - ``` - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 3333 - 5573 | 2162 | 3333 - (2 rows) - ``` - - 会话1 --先提交 - - ``` - postgres=# commit; - COMMIT - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 9999 - 5573 | 2162 | 9999 - (2 rows) - ``` - - 会话2 --不提交，查询依然o\_id=3333的数据 - - ``` - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 3333 - 5573 | 2162 | 3333 - (2 rows) - ``` - - 会话2 --后提交 - - ``` - postgres=# commit; - WARNING: AbortTransaction while in COMMIT state - ERROR: Commit: could not serialize access due to concurrent update(0) - postgres=# select * from mot_2 where o_w_id = 5573; - o_w_id | o_d_id | o_id - --------+--------+------ - 5573 | 8453 | 9999 - 5573 | 2162 | 9999 - (2 rows) - ``` - - insert\(commit和rollback\) - - 结论： - - 1、会话1做insert操作（commit之前），会话1可以查看新插入的数据，会话2无法查看到新插入的数据。 - - 2、等会话1做了commit之后，会话2可以看见新插入的数据。 - - 会话1 - - ``` - postgres=# \set AUTOCOMMIT off - postgres=# select count(*) from mot_2; - count - ------- - 2000 - (1 row) - postgres=# insert into mot_2 select ceil(random()*(10000-1)+1),ceil(random()*(10000-10)+10),ceil(random()*(10000-100)+100) FROM generate_series(1,2000); - INSERT 0 2000 - postgres=# postgres=# select count(*) from mot_2; - count - ------- - 4000 - (1 row) - postgres=# commit; - COMMIT - ``` - - 会话2 - - ``` - postgres=# \set AUTOCOMMIT off - postgres=# select count(*) from mot_2; - count - ------- - 2000 - (1 row) - - postgres=# select count(*) from mot_2; - count - ------- - 4000 - (1 row) - ``` - - update\(commit和rollback\) - - 结论：和insert原理相同 - - 会话1 - - ``` - postgres=# select count(*) from mot_1 where o_w_id=2; - count - ------- - 21 - (1 row) - - postgres=# - postgres=# update mot_1 set o_all_local = 5555 where o_w_id=2; - UPDATE 21 - postgres=# select count(*) from mot_1 where o_w_id=2 and o_all_local =5555; - count - ------- - 21 - (1 row) - - postgres=# commit; - COMMIT - ``` - - 会话2 - - ``` - postgres=# select count(*) from mot_1 where o_w_id=2 and o_all_local =5555; - count - ------- - 0 - (1 row) - - postgres=# select count(*) from mot_1 where o_w_id=2 and o_all_local =5555; - count - ------- - 21 - (1 row) - ``` - - 数据库stop、start之后MOT表的数据是否存在。 - - 结论：数据库MOT表的数据依然存在 - - ``` - postgres=# select count(*) from mot_1; - count - -------- - 199959 - (1 row) - postgres=# select count(*) from mot_2; - count - ------- - 4000 - (1 row) - postgres-# \q - [omm@bms-f408-0001 ~]$ gs_om -t stop - Stopping cluster. - ========================================= - Successfully stopped cluster. - ========================================= - End stop cluster. - [omm@bms-f408-0001 ~]$ gs_om -t start - Starting cluster. - ========================================= - ========================================= - Successfully started. - [omm@bms-f408-0001 ~]$ gsql -d postgres -p26000 - gsql ((openGauss 1.0.1 build 3a33fded) compiled at 2020-11-04 15:58:51 commit 0 last mr ) - Non-SSL connection (SSL connection is recommended when requiring high-security) - Type "help" for help. - - postgres=# select count(*) from mot_1; - count - -------- - 199959 - (1 row) - - postgres=# select count(*) from mot_2; - count - ------- - 4000 - (1 row) - ``` - - 通过create table as 从实体表创建MOT表。 - - 结论：不支持 - - ``` - postgres=# create table tbl_1(aid integer not null,bid integer); - CREATE TABLE - postgres=# insert into tbl_1 values(1001,9001); - INSERT 0 1 - postgres=# create FOREIGN table mot_from_tbl_1 as select * from tbl_1; - ERROR: syntax error at or near "as" - LINE 1: create FOREIGN table mot_from_tbl_1 as select * from tbl_1; - ^ - postgres=# create table tbl_2 as select * from tbl_1; - ``` - - 通过create forrign table as 从MOT表创建MOT表 - - 结论：不支持 - - ``` - postgres=# create FOREIGN table mot_3 as select * from mot_2; - ERROR: syntax error at or near "as" - LINE 1: create FOREIGN table mot_3 as select * from mot_2; - ^ - postgres=# create FOREIGN table mot_3 select * from mot_2; - ERROR: syntax error at or near "select" - LINE 1: create FOREIGN table mot_3 select * from mot_2; - ``` - - MOT表相互通过insert into select的方式插入数据。 - - 结论：支持 - - ``` - postgres=# create FOREIGN table mot_3 - postgres-# (o_w_id integer not null, - postgres(# o_d_id integer not null, - postgres(# o_id integer not null); - CREATE FOREIGN TABLE - postgres=# insert into mot_3 select * from mot_2; - INSERT 0 4000 - postgres=# commit; - ``` - - 通过insert into select 的方式从普通表向MOT表插入数据。 - - 结论：不支持 - - ``` - postgres=# create table tbl_1(aid integer not null,bid integer); - ERROR: relation "tbl_1" already exists - postgres=# insert into tbl_1 values(1001,9001); - INSERT 0 1 - postgres=# create FOREIGN table mot_tbl_1(aid integer not null,bid integer); - CREATE FOREIGN TABLE - postgres=# select count(*) from mot_tbl_1; - count - ------- - 0 - (1 row) - - postgres=# insert into mot_tbl_1 select * from tbl_1; - ERROR: Cross storage engine query is not supported - ``` - - openGauss MOT和其它数据库相关特性对比 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

序号

-

对比项

-

MOT

-

In Memory

-

1

-

数据存储方式

-

行

-

行、列

-

2

-

将磁盘表的数据直接转换到内存

-

û

-

ü

-

3

-

对内存表压缩

-

û

-

ü

-

4

-

分区

-

û

-

ü

-

5

-

truncate 支持rollback

-

ü

-

未知

-

6

-

乐观锁

-

ü

-

未知

-

7

-

支持多表关联查询

-

ü

-

ü

-

8

-

允许更新索引列

-

û

-

未知

-

9

-

数据库重启后内存数据依然保留

-

ü

-

ü

-
- - >![](public_sys-resources/icon-note.gif) **说明：** - >在关系数据库管理系统里，乐观并发控制（又名“乐观锁”，Optimistic Concurrency Control，缩写“OCC”）是一种并发控制的方法。它假设多用户并发的事务在处理时不会彼此互相影响，各事务能够在不产生锁的情况下处理各自影响的那部分数据。在提交数据更新之前，每个事务会先检查在该事务读取数据后，有没有其他事务又修改了该数据。 - -