[SPARK-47786] SELECT DISTINCT (*) should not become SELECT DISTINCT struct(*) (revert to previous behavior) #45970
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What changes were proposed in this pull request?
We special case SELECT DISTINCT () to become SELECT DISTINCT *
This prevents () to be treated as struct().
We used to ignore parens around stars () everywhere, but that is inconsistent with e.g. (c1, c2).
However there seems to be a reasonable number of users treating DISTINCT as a function.
Why are the changes needed?
Prevent regression for a common weird case.
Does this PR introduce any user-facing change?
No, It undoes a user changing change
How was this patch tested?
Existing QA, added new tests to selectExcept.sql
Was this patch authored or co-authored using generative AI tooling?
No