[GitHub] [spark] ulysses-you commented on a diff in pull request #38176: [SPARK-40715][SQL] Support selecting shuffled hash join thought LocalMapThreshold is less than advisory partition size

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

ulysses-you commented on code in PR #38176:
URL: https://github.com/apache/spark/pull/38176#discussion_r994485856


##########
sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/DynamicJoinSelection.scala:
##########
@@ -89,13 +111,19 @@ object DynamicJoinSelection extends Rule[LogicalPlan] with JoinSelectionHelper {
           false
         }
 
-        val preferShuffleHash = preferShuffledHashJoin(stage.mapStats.get)
+        val preferShuffleHash = streamedPlan match {
+          case LogicalQueryStage(_, streamedStage: ShuffleQueryStageExec)
+            if streamedStage.isMaterialized && streamedStage.mapStats.isDefined =>
+            preferShuffledHashJoin(stage.mapStats.get, streamedStage.mapStats.get)
+
+          case _ => false

Review Comment:
   this will be regression.. it prevents multi-join convert to shj, e.g.:
   
   ```
   SortMergejoin 2
     SortMergeJoin 1
       Shuffle 1
       Shuffle 2
     Shuffe 3
   ```
   The join 2 can not convert to shj even shuffle 3 is small



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