Github user liancheng commented on a diff in the pull request: https://github.com/apache/spark/pull/14106#discussion_r70584787 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala --- @@ -165,36 +165,48 @@ object PushProjectThroughSample extends Rule[LogicalPlan] { * but can also benefit other operators. */ object RemoveAliasOnlyProject extends Rule[LogicalPlan] { - // Check if projectList in the Project node has the same attribute names and ordering - // as its child node. + /** + * Returns true if the project list is semantically same with child output, after strip alias on + * attribute. + */ private def isAliasOnly( projectList: Seq[NamedExpression], childOutput: Seq[Attribute]): Boolean = { - if (!projectList.forall(_.isInstanceOf[Alias]) || projectList.length != childOutput.length) { + if (projectList.length != childOutput.length) { false } else { - projectList.map(_.asInstanceOf[Alias]).zip(childOutput).forall { case (a, o) => - a.child match { - case attr: Attribute if a.name == attr.name && attr.semanticEquals(o) => true - case _ => false - } + stripAliasOnAttribute(projectList).zip(childOutput).forall { + case (a: Attribute, o) if a semanticEquals o => true + case _ => false } } } + private def stripAliasOnAttribute(projectList: Seq[NamedExpression]) = { + projectList.map { + // Alias with metadata can not be striped, or the metadata will be lost. --- End diff -- Nit: striped => stripped
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