[GitHub] [spark] viirya commented on a change in pull request #34034: [SPARK-36794][SQL] Ignore duplicated join keys when building relation for SEMI/ANTI hash join

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

viirya commented on a change in pull request #34034:
URL: https://github.com/apache/spark/pull/34034#discussion_r716897033



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashJoin.scala
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@@ -158,6 +158,17 @@ trait HashJoin extends JoinCodegenSupport {
         output, (streamedPlan.output ++ buildPlan.output).map(_.withNullability(true)))
   }
 
+  // Exposed for testing
+  @transient lazy val ignoreDuplicatedKey = joinType match {
+    case LeftExistence(_) =>
+      // For building hash relation, ignore duplicated rows with same join keys if:
+      // 1. Join condition is empty.
+      // 2. Join condition only references streamed attributes and build join keys.

Review comment:
       We only need to meet any one requirement? So maybe say 
   
   ```
   1. Join condition is empty, or
   2. ...
   ```




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