Ngone51 commented on a change in pull request #29166:
URL: https://github.com/apache/spark/pull/29166#discussion_r457918626
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
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@@ -1192,11 +1192,23 @@ class Analyzer(
if
findAliases(projectList).intersect(conflictingAttributes).nonEmpty =>
Seq((oldVersion, oldVersion.copy(projectList =
newAliases(projectList))))
+ // We don't need to search child plan recursively if the projectList
of a Project
+ // is only composed of Alias and doesn't contain any conflicting
attributes.
+ // Because, even if the child plan has some conflicting attributes,
the attributes
+ // will be aliased to non-conflicting attributes by the Project at the
end.
+ case _ @ Project(projectList, _)
+ if findAliases(projectList).size == projectList.size =>
+ Nil
Review comment:
I think we don't. It's mutually exclusive with the previous one as it
has an implicit requirement (
`findAliases(projectList).intersect(conflictingAttributes).isEmpty`).
Therefore, the actual requirement here is:
`findAliases(projectList).intersect(conflictingAttributes).isEmpty &&
findAliases(projectList).size == projectList.size`
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