[GitHub] [spark] wangyum commented on a diff in pull request #36909: [SPARK-39511][SQL] Push down limit 1 for right side of left semi/anti join if join condition is empty

[GitBox <gi...@apache.org>]

wangyum commented on code in PR #36909:
URL: https://github.com/apache/spark/pull/36909#discussion_r902231084


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala:
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@@ -753,6 +753,9 @@ object LimitPushDown extends Rule[LogicalPlan] {
     // Merge offset value and limit value into LocalLimit and pushes down LocalLimit through Offset.
     case LocalLimit(le, Offset(oe, grandChild)) =>
       Offset(oe, LocalLimit(Add(le, oe), grandChild))
+    // Push down limit 1 if join type is LeftSemiOrAnti and join condition is empty
+    case j @ Join(_, right, LeftSemiOrAnti(_), None, _) if !right.maxRows.exists(_ <= 1) =>

Review Comment:
   To support queries do not contain limit. For example:
   ```sql
   SELECT * FROM v1 WHERE type IN (SELECT type FROM t2)
   ```



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