[GitHub] gatorsmile commented on a change in pull request #23343: [SPARK-26390][SQL] ColumnPruning rule should only do column pruning

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gatorsmile commented on a change in pull request #23343: [SPARK-26390][SQL] ColumnPruning rule should only do column pruning
URL: https://github.com/apache/spark/pull/23343#discussion_r242753230
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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 @@ -602,17 +606,11 @@ object ColumnPruning extends Rule[LogicalPlan] {
       p.copy(child = w.copy(
         windowExpressions = w.windowExpressions.filter(p.references.contains)))
 
-    // Eliminate no-op Window
-    case w: Window if w.windowExpressions.isEmpty => w.child
-
-    // Eliminate no-op Projects
-    case p @ Project(_, child) if child.sameOutput(p) => child
-
     // Can't prune the columns on LeafNode
     case p @ Project(_, _: LeafNode) => p
 
     // for all other logical plans that inherits the output from it's children
-    case p @ Project(_, child) =>
+    case p @ Project(_, child) if !child.isInstanceOf[Project] =>
 
 Review comment:
   This requires a code comment. I believe the others will ask the same q when we read the problem again. 

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