[GitHub] [spark] viirya commented on a change in pull request #30245: [SPARK-33337][SQL] Support subexpression elimination in branches of conditional expressions

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

viirya commented on a change in pull request #30245:
URL: https://github.com/apache/spark/pull/30245#discussion_r518419317



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -96,8 +131,21 @@ class EquivalentExpressions {
       case other => other.children
     }
 
-    if (!skip && !addExpr(expr)) {
-      childrenToRecurse.foreach(addExprTree)
+    // For some special expressions we cannot just recurse into all of its children, but we can
+    // recursively add the common expressions shared between all of its children.
+    def commonChildrenToRecurse: Seq[Seq[Expression]] = expr match {

Review comment:
       Ok.




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