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Richard Guo 5c214b58b0 Consider opfamily and collation when removing redundant GROUP BY columns ... remove_useless_groupby_columns() uses a relation's unique indexes to prove that some GROUP BY columns are functionally dependent on others, and so can be dropped from the GROUP BY clause. The match between index columns and GROUP BY columns was done by attno alone, ignoring two equality-relation issues. A type may belong to multiple btree opfamilies whose notions of equality differ. The record type, for instance, has record_ops (per-field equality) and record_image_ops (bytewise equality). A unique index under one opfamily does not prove uniqueness under the equality used by GROUP BY when the SortGroupClause's eqop comes from a different opfamily. Likewise, since nondeterministic collations were introduced in PG 12, two collations may disagree on equality, and a unique index under one collation does not prove uniqueness under another. In either case, rows that the index considers distinct can collapse into a single GROUP BY group, taking ungrouped columns of differing values with them, so the planner drops a column that is not in fact functionally dependent and produces wrong results. Fix by requiring, for each unique-index key column, that some GROUP BY item on the same column has an eqop in the index's opfamily and a collation that agrees on equality with the index's collation. This mirrors the combined check relation_has_unique_index_for() applies to join clauses. This is a v18 regression: commit bd10ec529 extended remove_useless_groupby_columns() from primary-key constraints to arbitrary unique indexes. Before that, the function consulted only primary keys, whose enforcement index is required by parse_utilcmd.c to use the default opclass and the column's declared collation, so neither mismatch could arise. Back-patch to v18 only. Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com> Discussion: https://postgr.es/m/CAMbWs49t6uArWoTT-cHY+nhsi23nJJKcF9Xb9cYGzaZ9kNJ98g@mail.gmail.com Backpatch-through: 18		1 month ago
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backend	Consider opfamily and collation when removing redundant GROUP BY columns	1 month ago
bin	pg_test_timing: fix unit in backward-clock warning	2 months ago
common	Fix callers of unicode_strtitle() using srclen == -1.	2 months ago
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include	Add missing guard for __builtin_constant_p	1 month ago
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makefiles	pgxs.mk: remove unreachable rule for deleting regress.def.	12 months ago
pl	Make plpgsql_trap test more robust and less resource-intensive.	2 months ago
port	Suppress "has no symbols" linker warnings on macOS.	1 month ago
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test	Consider opfamily and collation when removing redundant GROUP BY columns	1 month ago
timezone	Update time zone data files to tzdata release 2026b.	2 months ago
tools	Consider opfamily and collation when removing redundant GROUP BY columns	1 month ago
tutorial	Doc: simplify the tutorial's window-function examples.	1 year ago
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Makefile	…
Makefile.global.in	Don't put library-supplied -L/-I switches before user-supplied ones.	11 months ago
Makefile.shlib	Use exported symbols list on macOS for loadable modules as well	1 year ago
meson.build	…
nls-global.mk	Fix update-po for the PGXS case	8 months ago