Support DISTINCT ON with aggregation and windows#22169
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Which issue does this PR close?
Rationale for this change
DataFusion currently rejects
DISTINCT ONqueries when they are combined withGROUP BY, aggregate functions, or window functions.PostgreSQL allows these queries. The planner already builds the aggregate and window plan before applying
DISTINCT ON, but the oldDISTINCT ONpath only worked against the pre-aggregation input. That meant expressions that depended on aggregate or window output could not be planned.What changes are included in this PR?
This PR updates
DISTINCT ONplanning so its expressions participate in the same aggregate and window rewrite pipeline asSELECT,HAVING,QUALIFY, andORDER BY.It also keeps hidden
DISTINCT ONkeys andORDER BYtie-breakers in scope before the final projection, so valid PostgreSQL-style queries work even when those expressions are not in the select list.The change also handles SELECT alias resolution for
DISTINCT ONandORDER BYin the PostgreSQL-compatible way: a bare alias can resolve to the select expression, while the same name inside a larger expression still resolves as an input column.Are these changes tested?
Yes
Are there any user-facing changes?
No public API Change