[GitHub] [spark] seanli-rallyhealth commented on a change in pull request #27436: [SPARK-30705][SQL] Improve CaseWhen sub-expression equality

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seanli-rallyhealth commented on a change in pull request #27436: [SPARK-30705][SQL] Improve CaseWhen sub-expression equality
URL: https://github.com/apache/spark/pull/27436#discussion_r375576876
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
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 @@ -91,7 +91,18 @@ class EquivalentExpressions {
     def childrenToRecurse: Seq[Expression] = expr match {
       case _: CodegenFallback => Nil
       case i: If => i.predicate :: Nil
-      case c: CaseWhen => c.children.head :: Nil
+      case c: CaseWhen =>
+        val firstExpression = c.children.head
+        val firstUdes = firstExpression.collect { case u: UserDefinedExpression => u }
+        val accessedExpressions = c.children.filter { e =>
+          val udes = e.collect { case u: UserDefinedExpression => u }
+          udes.nonEmpty && firstUdes.containsSlice(udes)
+        }
+        if (accessedExpressions.nonEmpty) {
 
 Review comment:
   don't think accessedExpressions will be empty since firstExpression is always inside.

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