viirya commented on a change in pull request #28898:
URL: https://github.com/apache/spark/pull/28898#discussion_r448753272
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/NestedColumnAliasing.scala
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@@ -172,13 +188,23 @@ object NestedColumnAliasing {
(f, Alias(f, s"_gen_alias_${exprId.id}")(exprId, Seq.empty, None))
}
+
+ // Do deduplication based on semanticEquals, and then sum.
+ val nestedFieldNum = nestedFieldToAlias
+ .foldLeft(Seq[ExtractValue]()) {
+ (unique, curr) => if (!unique.exists(curr._1.semanticEquals(_))) {
+ curr._1 +: unique
+ } else {
+ unique
+ }
+ }
+ .map { t => totalFieldNum(t.dataType) }
+ .sum
Review comment:
The problem in your approach is, which one is selected from the
`ExtractValue`s with different qualifier, is non-deterministic.
Later when we query the `nestedFieldToAlias` map, you might fail to find the
corresponding item from the map due to qualifier difference.
I think the safer approach is to clean up all qualifier.
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