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pgsql: Don't flatten join alias Vars that are stored within a GROUP RTE 2+ messages / 1 participants [nested] [flat]
* pgsql: Don't flatten join alias Vars that are stored within a GROUP RTE @ 2026-02-27 17:54 Tom Lane <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2026-02-27 17:54 UTC (permalink / raw) To: [email protected] Don't flatten join alias Vars that are stored within a GROUP RTE. The RTE's groupexprs list is used for deparsing views, and for that usage it must contain the original alias Vars; else we can get incorrect SQL output. But since commit 247dea89f, parseCheckAggregates put the GROUP BY expressions through flatten_join_alias_vars before building the RTE_GROUP RTE. Changing the order of operations there is enough to fix it. This patch unfortunately can do nothing for already-created views: if they use a coding pattern that is subject to the bug, they will deparse incorrectly and hence present a dump/reload hazard in the future. The only fix is to recreate the view from the original SQL. But the trouble cases seem to be quite narrow. AFAICT the output was only wrong for "SELECT ... t1 LEFT JOIN t2 USING (x) GROUP BY x" where t1.x and t2.x were not of identical data types and t1.x was the side that required an implicit coercion. If there was no hidden coercion, or if the join was plain, RIGHT, or FULL, the deparsed output was uglier than intended but not functionally wrong. Reported-by: Swirl Smog Dowry <[email protected]> Author: Tom Lane <[email protected]> Reviewed-by: Richard Guo <[email protected]> Discussion: https://postgr.es/m/CA+-gibjCg_vjcq3hWTM0sLs3_TUZ6Q9rkv8+pe2yJrdh4o4uoQ@mail.gmail.com Backpatch-through: 18 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/c2c1962a64b547412c88fa2728e4fa35e65f4c90 Modified Files -------------- src/backend/parser/parse_agg.c | 36 +++++++++++++++++--------------- src/test/regress/expected/aggregates.out | 13 ++++++++++++ src/test/regress/sql/aggregates.sql | 6 ++++++ 3 files changed, 38 insertions(+), 17 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
* pgsql: Don't flatten join alias Vars that are stored within a GROUP RTE @ 2026-02-27 17:54 Tom Lane <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2026-02-27 17:54 UTC (permalink / raw) To: [email protected] Don't flatten join alias Vars that are stored within a GROUP RTE. The RTE's groupexprs list is used for deparsing views, and for that usage it must contain the original alias Vars; else we can get incorrect SQL output. But since commit 247dea89f, parseCheckAggregates put the GROUP BY expressions through flatten_join_alias_vars before building the RTE_GROUP RTE. Changing the order of operations there is enough to fix it. This patch unfortunately can do nothing for already-created views: if they use a coding pattern that is subject to the bug, they will deparse incorrectly and hence present a dump/reload hazard in the future. The only fix is to recreate the view from the original SQL. But the trouble cases seem to be quite narrow. AFAICT the output was only wrong for "SELECT ... t1 LEFT JOIN t2 USING (x) GROUP BY x" where t1.x and t2.x were not of identical data types and t1.x was the side that required an implicit coercion. If there was no hidden coercion, or if the join was plain, RIGHT, or FULL, the deparsed output was uglier than intended but not functionally wrong. Reported-by: Swirl Smog Dowry <[email protected]> Author: Tom Lane <[email protected]> Reviewed-by: Richard Guo <[email protected]> Discussion: https://postgr.es/m/CA+-gibjCg_vjcq3hWTM0sLs3_TUZ6Q9rkv8+pe2yJrdh4o4uoQ@mail.gmail.com Backpatch-through: 18 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/98616ac18b49ac9f84a96177d8a7822f34904183 Modified Files -------------- src/backend/parser/parse_agg.c | 36 +++++++++++++++++--------------- src/test/regress/expected/aggregates.out | 13 ++++++++++++ src/test/regress/sql/aggregates.sql | 6 ++++++ 3 files changed, 38 insertions(+), 17 deletions(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2026-02-27 17:54 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-02-27 17:54 pgsql: Don't flatten join alias Vars that are stored within a GROUP RTE Tom Lane <[email protected]> 2026-02-27 17:54 pgsql: Don't flatten join alias Vars that are stored within a GROUP RTE Tom Lane <[email protected]>
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