[GitHub] [spark] dongjoon-hyun commented on a change in pull request #24837: [SPARK-27917][SQL][BACKPORT-2.3] canonical form of CaseWhen object is incorrect

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

dongjoon-hyun commented on a change in pull request #24837: [SPARK-27917][SQL][BACKPORT-2.3] canonical form of CaseWhen object is incorrect
URL: https://github.com/apache/spark/pull/24837#discussion_r292281227
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
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 @@ -199,44 +199,33 @@ abstract class TreeNode[BaseType <: TreeNode[BaseType]] extends Product {
     var changed = false
     val remainingNewChildren = newChildren.toBuffer
     val remainingOldChildren = children.toBuffer
+    def mapTreeNode(node: TreeNode[_]): TreeNode[_] = {
+      val newChild = remainingNewChildren.remove(0)
+      val oldChild = remainingOldChildren.remove(0)
+      if (newChild fastEquals oldChild) {
+        oldChild
+      } else {
+        changed = true
+        newChild
+      }
+    }
+    def mapChild(child: Any): Any = child match {
+      case arg: TreeNode[_] if containsChild(arg) => mapTreeNode(arg)
+      // CaseWhen Case or any tuple type
+      case (left, right) => (mapChild(left), mapChild(right))
+      case nonChild: AnyRef => nonChild
+      case null => null
+    }
 
 Review comment:
   Wow, it looks too risk backport..

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