[GitHub] [spark] allisonwang-db commented on a change in pull request #32072: [SPARK-34974][SQL] Improve subquery decorrelation framework

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

allisonwang-db commented on a change in pull request #32072:
URL: https://github.com/apache/spark/pull/32072#discussion_r612695929



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/subquery.scala
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@@ -173,18 +170,16 @@ object SubExprUtils extends PredicateHelper {
    * }}}
    * The code below needs to change when we support the above cases.
    */
-  def getOuterReferences(conditions: Seq[Expression]): Seq[Expression] = {
+  def getOuterReferences(condition: Expression): Seq[Expression] = {
     val outerExpressions = ArrayBuffer.empty[Expression]
-    conditions foreach { expr =>
-      expr transformDown {
-        case a: AggregateExpression if a.collectLeaves.forall(_.isInstanceOf[OuterReference]) =>
-          val newExpr = stripOuterReference(a)
-          outerExpressions += newExpr
-          newExpr
-        case OuterReference(e) =>
-          outerExpressions += e
-          e
-      }
+    condition transformDown {

Review comment:
       This `transformDown` is actually needed. It updates the aggregate expression so that the outer references inside this aggregate expression will not be collected. I've added a comment.




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