Because we failed to do this, DISTINCT in GROUP BY DISTINCT would be ignored in PL/pgSQL assignment statements. It's not surprising that no one noticed, since such statements will throw an error if the query produces more than one row. That eliminates most scenarios where advanced forms of GROUP BY could be useful, and indeed makes it hard even to find a simple test case. Nonetheless it's wrong. This is directly the fault ofbe45be9c3
which added the groupDistinct field, but I think much of the blame has to fall onc9d529848
, in which I incautiously supposed that we'd manage to keep two copies of a big chunk of parse-analysis logic in sync. As a follow-up, I plan to refactor so that there's only one copy. But that seems useful only in master, so let's use this one-line fix for the back branches. Author: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/31027.1758919078@sss.pgh.pa.us Backpatch-through: 14
PostgreSQL Database Management System
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