Thread: [COMMITTERS] pgsql: Prevent sharing transition states between ordered-setaggregates
[COMMITTERS] pgsql: Prevent sharing transition states between ordered-setaggregates
From
Tom Lane
Date:
Prevent sharing transition states between ordered-set aggregates. This ought to work, but the built-in OSAs are not capable of coping, because their final-functions destructively modify their transition state (specifically, the contained tuplesort object). That was fine when those functions were written, but commit 804163bc2 moved the goalposts without telling orderedsetaggs.c. We should fix the built-in OSAs to support this, but it will take a little work, especially if we don't want to sacrifice performance in the normal non-shared-state case. Given that it took a year after 9.6 release for anyone to notice this bug, we should not prioritize sharable-state over nonsharable-state performance. And a proper fix is likely to be more complicated than we'd want to back-patch, too. Therefore, let's just put in this stop-gap patch to prevent nodeAgg.c from choosing to use shared state for OSAs. We can revert it in HEAD when we get a better fix. Report from Lukas Eder, diagnosis by me, patch by David Rowley. Back-patch to 9.6 where the problem was introduced. Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com Branch ------ REL_10_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/604723d29a86f38551e43997e6f40daa94f54b27 Modified Files -------------- src/backend/executor/nodeAgg.c | 10 ++++++++++ src/test/regress/expected/aggregates.out | 19 +++++++++++++++++++ src/test/regress/sql/aggregates.sql | 11 +++++++++++ 3 files changed, 40 insertions(+) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers