viirya commented on a change in pull request #31595: URL: https://github.com/apache/spark/pull/31595#discussion_r579720302
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala ########## @@ -492,12 +492,43 @@ object RemoveRedundantAliases extends Rule[LogicalPlan] { * Remove no-op operators from the query plan that do not make any modifications. */ object RemoveNoopOperators extends Rule[LogicalPlan] { + private def removeAliasOnlyProject(plan: LogicalPlan): LogicalPlan = plan match { + case p @ Project(projectList, child) => + val originalOutputs = projectList.collect { + case Alias(a: Attribute, _) => a + case a: Attribute => a + } + if (child.outputSet.nonEmpty && child.outputSet == AttributeSet(originalOutputs)) { + child + } else { + p + } + case _ => plan + } + def apply(plan: LogicalPlan): LogicalPlan = plan transformUp { // Eliminate no-op Projects case p @ Project(_, child) if child.sameOutput(p) => child // Eliminate no-op Window case w: Window if w.windowExpressions.isEmpty => w.child + + // Eliminate no-op Union + case d @ Distinct(u: Union) => + val unionChildren = u.children.map(c => removeAliasOnlyProject(c)) + if (unionChildren.tail.forall(unionChildren.head.sameResult(_))) { + d.withNewChildren(Seq(u.children.head)) + } else { + d + } + + case d @ Deduplicate(keys: Seq[Attribute], u: Union) if AttributeSet(keys) == u.outputSet => Review comment: You're correct. Thanks. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org