[GitHub] [spark] mgaido91 commented on a change in pull request #24214: [SPARK-27279][SQL] Reuse subquery should compare child plan of `SubqueryExec`

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mgaido91 commented on a change in pull request #24214: [SPARK-27279][SQL] Reuse subquery should compare child plan of `SubqueryExec`
URL: https://github.com/apache/spark/pull/24214#discussion_r269133230
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/subquery.scala
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 @@ -125,15 +125,15 @@ case class PlanSubqueries(sparkSession: SparkSession) extends Rule[SparkPlan] {
 case class ReuseSubquery(conf: SQLConf) extends Rule[SparkPlan] {
 
   def apply(plan: SparkPlan): SparkPlan = {
-    if (!conf.exchangeReuseEnabled) {
+    if (!conf.subqueryReuseEnabled) {
       return plan
     }
     // Build a hash map using schema of subqueries to avoid O(N*N) sameResult calls.
     val subqueries = mutable.HashMap[StructType, ArrayBuffer[SubqueryExec]]()
     plan transformAllExpressions {
       case sub: ExecSubqueryExpression =>
         val sameSchema = subqueries.getOrElseUpdate(sub.plan.schema, ArrayBuffer[SubqueryExec]())
-        val sameResult = sameSchema.find(_.sameResult(sub.plan))
+        val sameResult = sameSchema.find(_.child.sameResult(sub.plan.child))
 
 Review comment:
   I am not sure either about this fix. I remember this problem which I tried to fix in https://github.com/apache/spark/pull/22518/commits/36fa664c6d251901270984115ff2ebfd1b665fca. As you can see, the PR didn't actually do this fix as per @cloud-fan 's comment. So I am pinging him here for reviewing this too. Anyway, when I debugged it, the problem was that being the same object according to equals, the tree was not updated, so I see no reason for the current fix.

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