Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/9409#discussion_r44215590
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Utils.scala
---
@@ -54,10 +54,14 @@ object Utils {
mode = aggregate.Complete,
isDistinct = false)
- // We do not support multiple COUNT DISTINCT columns for now.
- case expressions.CountDistinct(children) if children.length == 1 =>
+ case expressions.CountDistinct(children) =>
+ val child = if (children.size > 1) {
+ DropAnyNull(CreateStruct(children))
--- End diff --
oh, yes. Based on
https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala#L240-L266,
we can compare two struct values. Looks like only array and map types are not
handled there. So, I think we can visit all data types of a struct and if it
does not have array or map, we can use new agg code path. Can you update
Utils.scala? I am thinking about if an array or a map appear in the grouping
expressions, we throw an analysis error and say it is not allowed right now.
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