diff --git a/omnidata/omnidata-spark-connector/connector/src/main/java/com/huawei/boostkit/omnidata/spark/PageDeRunLength.java b/omnidata/omnidata-spark-connector/connector/src/main/java/com/huawei/boostkit/omnidata/spark/PageDeRunLength.java
index f0c8c1fc282a8dc471178bf5f9db98f7172f3761..52cd6b1ecaff38e53bb491d62c6d59cd88387517 100644
--- a/omnidata/omnidata-spark-connector/connector/src/main/java/com/huawei/boostkit/omnidata/spark/PageDeRunLength.java
+++ b/omnidata/omnidata-spark-connector/connector/src/main/java/com/huawei/boostkit/omnidata/spark/PageDeRunLength.java
@@ -264,7 +264,7 @@ public class PageDeRunLength {
         WritableColumnVector columnVector = getColumnVector(isOperatorCombineEnabled, positionCount,
                 writableColumnVector);
         for (int rowId = 0; rowId < positionCount; rowId++) {
-            if (writableColumnVector.isNullAt(rowId)) {
+            if (writableColumnVector.isNullAt(rowId) || value == null) {
                 columnVector.putNull(rowId);
             } else {
                 columnVector.putDecimal(rowId, value, precision);
diff --git a/omnidata/omnidata-spark-connector/connector/src/main/java/org/apache/spark/sql/DataIoAdapter.java b/omnidata/omnidata-spark-connector/connector/src/main/java/org/apache/spark/sql/DataIoAdapter.java
index 0a9270ca0cf8ebee67550c250299b22ec7d86801..ae4312aa60a4e10fcde38f5041335475d4de2b72 100644
--- a/omnidata/omnidata-spark-connector/connector/src/main/java/org/apache/spark/sql/DataIoAdapter.java
+++ b/omnidata/omnidata-spark-connector/connector/src/main/java/org/apache/spark/sql/DataIoAdapter.java
@@ -215,11 +215,20 @@ public class DataIoAdapter {
         PageDeserializer deserializer = initPageDeserializer();
 
         // get available host
-        String[] pushDownHostArray = pageCandidate.getpushDownHosts().split(",");
-        List<String> pushDownHostList = new ArrayList<>(Arrays.asList(pushDownHostArray));
-        Optional<String> availablePushDownHost = getRandomAvailablePushDownHost(pushDownHostArray,
-                JavaConverters.mapAsJavaMap(pushDownOperators.fpuHosts()));
-        availablePushDownHost.ifPresent(pushDownHostList::add);
+        List<String> pushDownHostList = new ArrayList<>();
+        String[] pushDownHostArray;
+        if (pageCandidate.getpushDownHosts().length() == 0) {
+            Optional<String> availablePushDownHost = getRandomAvailablePushDownHost(new String[]{},
+                    JavaConverters.mapAsJavaMap(pushDownOperators.fpuHosts()));
+            availablePushDownHost.ifPresent(pushDownHostList::add);
+            pushDownHostArray = pushDownHostList.toArray(new String[]{});
+        } else {
+            pushDownHostArray = pageCandidate.getpushDownHosts().split(",");
+            pushDownHostList = new ArrayList<>(Arrays.asList(pushDownHostArray));
+            Optional<String> availablePushDownHost = getRandomAvailablePushDownHost(pushDownHostArray,
+                    JavaConverters.mapAsJavaMap(pushDownOperators.fpuHosts()));
+            availablePushDownHost.ifPresent(pushDownHostList::add);
+        }
         return getIterator(pushDownHostList.iterator(), taskSource, pushDownHostArray, deserializer,
                 pushDownHostList.size());
     }
@@ -282,8 +291,9 @@ public class DataIoAdapter {
         List<String> allHosts = new ArrayList<>(fpuHosts.values());
         allHosts.removeAll(existingHosts);
         if (allHosts.size() > 0) {
-            LOG.info("Add another available host: " + allHosts.get(0));
-            return Optional.of(allHosts.get(0));
+            int randomIndex = (int) (Math.random() * allHosts.size());
+            LOG.info("Add another available host: " + allHosts.get(randomIndex));
+            return Optional.of(allHosts.get(randomIndex));
         } else {
             return Optional.empty();
         }