d446ca2c45
query_is_distinct_for() treated a subquery's DISTINCT ON clause as proof that its output is unique over the DISTINCT ON columns, even if the targetlist contains set-returning functions. That's not true: when the query has an ORDER BY, the planner postpones evaluation of SRFs that are not DISTINCT ON or ORDER BY columns until after the Unique step, so the subquery can produce duplicates of the DISTINCT ON columns. Relying on this bogus uniqueness proof allowed join removal and unique-inner joins to produce wrong results. Plain DISTINCT is not affected, since all tlist columns are DISTINCT columns there, and so any SRFs get expanded before the Unique step. To fix, make query_supports_distinctness() and query_is_distinct_for() refuse to prove distinctness via DISTINCT ON if the targetlist contains any SRFs. This is more conservative than necessary, since the SRFs are only postponed when there is an ORDER BY and none of them appear in a sort/group column, but it doesn't seem worth the trouble to check that precisely. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAMbWs4-hfd1Pyy_zBejsVUSy-3dx16rz2hgUakkKnAg3qg2q=Q@mail.gmail.com Backpatch-through: 14
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/19/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/19/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.