maropu commented on a change in pull request #24525: [SPARK-27633][SQL] Remove
redundant aliases in NestedColumnAliasing
URL: https://github.com/apache/spark/pull/24525#discussion_r315461919
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/NestedColumnAliasing.scala
##########
@@ -119,9 +119,21 @@ object NestedColumnAliasing {
.filter(!_.references.subsetOf(AttributeSet(otherRootReferences)))
.groupBy(_.references.head)
.flatMap { case (attr, nestedFields: Seq[ExtractValue]) =>
+ // Remove redundant `ExtractValue`s if they share the same parent nest
field.
+ // For example, when `a.b` and `a.b.c` are in project list, we only
need to alias `a.b`.
+ // We only need to deal with two `ExtractValue`:
`GetArrayStructFields` and
+ // `GetStructField`. Please refer to the method
`collectRootReferenceAndExtractValue`.
+ val dedupNestedFields = nestedFields.filter {
+ case a @ GetArrayStructFields(child, _, _, _, _) =>
+ nestedFields.forall(f => f == a ||
child.find(_.semanticEquals(f)).isEmpty)
+ case n @ GetStructField(child, _, _) =>
+ nestedFields.forall(f => f == n ||
child.find(_.semanticEquals(f)).isEmpty)
Review comment:
Thanks for the check! Ur, one more comment: can we avoid the loop of
`length(nestedFields)^2`? in:
https://github.com/apache/spark/pull/24525/files#diff-43334bab9616cc53e8797b9afa9fc7aaR129
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