[GitHub] maropu commented on a change in pull request #18576: [SPARK-21351][SQL] Update nullability based on children's output

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maropu commented on a change in pull request #18576: [SPARK-21351][SQL] Update nullability based on children's output
URL: https://github.com/apache/spark/pull/18576#discussion_r244072098
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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 @@ -153,7 +153,9 @@ abstract class Optimizer(sessionCatalog: SessionCatalog)
       RewritePredicateSubquery,
       ColumnPruning,
       CollapseProject,
-      RemoveRedundantProject)
+      RemoveRedundantProject) :+
+    Batch("UpdateAttributeReferences", Once,
+      UpdateNullabilityInAttributeReferences)
 
 Review comment:
   yea, I have the same opinion with @gatorsmile; `FixNullability` is related to the correctness, but `UpdateNullabilityInAttributeReferences` is not (just for optimization).
   
   @gatorsmile I think we haven't checked actual performance benefits (e.g., wall time) from the rule now. I just assume that this rule could generate better code from the code generator.

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