j-esse commented on a change in pull request #23556: [SPARK-26626][SQL] Maximum
size for repeatedly substituted aliases in SQL expressions
URL: https://github.com/apache/spark/pull/23556#discussion_r265745285
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -658,7 +658,8 @@ object CollapseProject extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
Review comment:
The purpose is to improve the rule so that it only applies when it will
yield a performance improvement (and not apply when it could cause memory
issues). This was the preferred solution, since if we excluded the rule
entirely we wouldn't benefit from it in the instances where it would be
beneficial.
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