[GitHub] [spark] cloud-fan commented on a change in pull request #30178: [SPARK-33278][SQL] Improve the performance for FIRST_VALUE

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

cloud-fan commented on a change in pull request #30178:
URL: https://github.com/apache/spark/pull/30178#discussion_r521388978



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -806,6 +807,18 @@ object CollapseRepartition extends Rule[LogicalPlan] {
   }
 }
 
+/**
+ * Substitute the aggregate expression which uses [[First]] as the aggregate function

Review comment:
       nit: `Replaces first(col) to nth_value(col, 1) for better performance.`




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