viirya commented on a change in pull request #28988:
URL: https://github.com/apache/spark/pull/28988#discussion_r449903754
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/NestedColumnAliasing.scala
##########
@@ -174,9 +176,12 @@ object NestedColumnAliasing {
// If all nested fields of `attr` are used, we don't need to introduce
new aliases.
// By default, ColumnPruning rule uses `attr` already.
+ // Note that we need to remove cosmetic variations first, so we only
count a
+ // nested field once.
if (nestedFieldToAlias.nonEmpty &&
- nestedFieldToAlias
- .map { case (nestedField, _) =>
totalFieldNum(nestedField.dataType) }
+ dedupNestedFields.map(_.canonicalized.asInstanceOf[ExtractValue])
Review comment:
For the duplicated aliases, we can avoid it. We can work on
canonicalized extractors when generating aliases.
But we also need to convert coming extractors to canonicalized versions when
we look up into the alias map.
Currently the code looks clear. And it seems not a big deal, and I think it
is rare case that there are multiple extractors with cosmetic difference. So
currently I don't try to do that.
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