c21 commented on a change in pull request #35216:
URL: https://github.com/apache/spark/pull/35216#discussion_r787253434
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -684,7 +684,9 @@ object LimitPushDown extends Rule[LogicalPlan] {
left = maybePushLocalLimit(limitExpr, join.left),
right = maybePushLocalLimit(limitExpr, join.right))
case LeftSemi | LeftAnti if join.condition.isEmpty =>
- join.copy(left = maybePushLocalLimit(limitExpr, join.left))
+ join.copy(
+ left = maybePushLocalLimit(limitExpr, join.left),
+ right = maybePushLocalLimit(Literal(1, IntegerType), join.right))
Review comment:
Actually I think this PR is orthogonal to what we have did during join
execution - https://github.com/apache/spark/pull/34247. During join execution,
the optimization was the only keeping one row per key in hash table of SHJ.
This optimizer rule here will affect join without condition, so the join would
be BNLJ or `CartesianProduct`.
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