[GitHub] [spark] cloud-fan commented on a change in pull request #24637: [SPARK-27707][SQL] Prune unnecessary nested fields from Generate to address performance issue in explode

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cloud-fan commented on a change in pull request #24637: [SPARK-27707][SQL] Prune unnecessary nested fields from Generate to address performance issue in explode
URL: https://github.com/apache/spark/pull/24637#discussion_r285869213
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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 @@ -588,6 +588,16 @@ object ColumnPruning extends Rule[LogicalPlan] {
         .map(_._2)
       p.copy(child = g.copy(child = newChild, unrequiredChildIndex = unrequiredIndices))
 
+    // prune unrequired nested fields
+    case p @ Project(projectList, g: Generate) =>
 
 Review comment:
   Why we need to special case `Generate`? I see there is a general case for nested column pruning below.

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