cloud-fan commented on a change in pull request #31595:
URL: https://github.com/apache/spark/pull/31595#discussion_r581012033
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -501,6 +502,42 @@ object RemoveNoopOperators extends Rule[LogicalPlan] {
}
}
+/**
+ * Remove no-op `Union` from the query plan that do not make any modifications.
+ */
+object RemoveNoopUnion extends Rule[LogicalPlan] {
+ private def removeAliasOnlyProject(plan: LogicalPlan): LogicalPlan = plan
match {
+ case p @ Project(projectList, child) =>
+ val originalOutputs = projectList.collect {
Review comment:
In addition to adding tests, can we also add comments to explain it?
`Project(a, a + 1 as res, Table(a))` is not alias-only but seems the code here
will remove the `Project`.
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