[GitHub] [spark] jchen5 commented on a diff in pull request #39375: [SPARK-36124][SQL] Support subqueries with correlation through UNION

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

jchen5 commented on code in PR #39375:
URL: https://github.com/apache/spark/pull/39375#discussion_r1067355121


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/DecorrelateInnerQuery.scala:
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@@ -667,6 +720,24 @@ object DecorrelateInnerQuery extends PredicateHelper {
             val newJoin = j.copy(left = newLeft, right = newRight, condition = newCondition)
             (newJoin, newJoinCond, newOuterReferenceMap)
 
+          case u: Union =>
+            // First collect outer references from all children
+            val collectedChildOuterReferences = collectOuterReferencesInPlanTree(u)

Review Comment:
   It's described with an example in the linked doc https://docs.google.com/document/d/11b9ClCF2jYGU7vU2suOT7LRswYkg6tZ8_6xJbvxfh2I/edit# - does that answer your question? I'll add the info to the comments as well.



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