[GitHub] [spark] wangyum commented on a change in pull request #26409: [SPARK-29655][SQL] Read bucketed tables obeys spark.sql.shuffle.partitions

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wangyum commented on a change in pull request #26409: [SPARK-29655][SQL] Read bucketed tables obeys spark.sql.shuffle.partitions
URL: https://github.com/apache/spark/pull/26409#discussion_r345273315
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala
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 @@ -83,7 +83,25 @@ case class EnsureRequirements(conf: SQLConf) extends Rule[SparkPlan] {
         numPartitionsSet.headOption
       }
 
-      val targetNumPartitions = requiredNumPartitions.getOrElse(childrenNumPartitions.max)
+      // maxNumPostShufflePartitions is usually larger than numShufflePartitions,
+      // which causes some bucket map join lose efficacy after enabling adaptive execution.
+      // Please see SPARK-29655 for more details.
+      val expectedChildrenNumPartitions = if (conf.adaptiveExecutionEnabled) {
 
 Review comment:
   What do you think of another implementation: https://github.com/apache/spark/pull/26409/commits/45109c71c3efc31f0d5aba6588a811faeea2a8f2? It may be more reasonable. But personally, I do not like add new conf.

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