maheshk114 commented on a change in pull request #1147:
URL: https://github.com/apache/hive/pull/1147#discussion_r459827002
##########
File path:
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveJoinAddNotNullRule.java
##########
@@ -74,7 +78,14 @@ public HiveJoinAddNotNullRule(Class<? extends Join> clazz,
@Override
public void onMatch(RelOptRuleCall call) {
Join join = call.rel(0);
- if (join.getJoinType() == JoinRelType.FULL ||
join.getCondition().isAlwaysTrue()) {
+
+ // For anti join case add the not null on right side if the condition is
+ // always true. This is done because during execution, anti join expect
the right side to
+ // be empty and if we dont put null check on right, for null only right
side table and condition
+ // always true, execution will produce 0 records.
+ // eg select * from left_tbl where (select 1 from all_null_right limit 1)
is null
+ if (join.getJoinType() == JoinRelType.FULL ||
+ (join.getJoinType() != JoinRelType.ANTI &&
join.getCondition().isAlwaysTrue())) {
Review comment:
Yes, the comment is not proper. It's like we will add a not null
condition for anti join even if the condition is always true.
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