cloud-fan commented on a change in pull request #29484:
URL: https://github.com/apache/spark/pull/29484#discussion_r473787293
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashJoin.scala
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@@ -442,7 +446,11 @@ trait HashJoin extends BaseJoinExec with CodegenSupport {
case BuildRight => input ++ buildVars
}
- if (keyIsUnique) {
+ if (isEmptyHashedRelation) {
+ s"""
+ |// If HashedRelation is empty, hash inner join simply returns
nothing.
Review comment:
We can keep this change, as it at least avoids looking up an empty hash
relation and is better than before. It's still useful with AQE is off.
We just need to add a new rule, or extend rule `EliminateNullAwareAntiJoin`
and rename it to `OptimizeJoinToEmptyRelation`.
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