From 001c09d8b72ee67ea670a1e9a534fa96948829dd Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 22 Jan 2025 11:58:20 -0500 Subject: Repair incorrect handling of AfterTriggerSharedData.ats_modifiedcols. This patch fixes two distinct errors that both ultimately trace to commit 71d60e2aa, which added the ats_modifiedcols field. The more severe error is that ats_modifiedcols wasn't accounted for in afterTriggerAddEvent's scanning loop that looks for a pre-existing duplicate AfterTriggerSharedData. Thus, a new event could be incorrectly matched to an AfterTriggerSharedData that has a different value of ats_modifiedcols, resulting in the wrong tg_updatedcols bitmap getting passed to the trigger whenever it finally gets fired. We'd not noticed because (a) few triggers consult tg_updatedcols, and (b) we had no tests exercising a case where such a trigger was called as an AFTER trigger. In the test case added by this commit, contrib/lo's trigger fails to remove a large object when expected because (without this fix) it thinks the LO OID column hasn't changed. The other problem was introduced by commit ce5aaea8c, which copied the modified-columns bitmap into trigger-related storage. It made a copy for every trigger event, whereas what we really want is to make a new copy only when we make a new AfterTriggerSharedData entry. (We could imagine adding extra logic to reduce the number of bitmap copies still more, but it doesn't look worthwhile at the moment.) In a simple test of an UPDATE of 10000000 rows with a single AFTER trigger, this thinko roughly tripled the amount of memory consumed by the pending-triggers data structures, from 160446744 to 480443440 bytes. Fixing the first problem requires introducing a bms_equal() call into afterTriggerAddEvent's scanning loop, which is slightly annoying from a speed perspective. However, getting rid of the excessive bms_copy() calls from the second problem balances that out; overall speed of trigger operations is the same or slightly better, in my tests. Discussion: https://postgr.es/m/3496294.1737501591@sss.pgh.pa.us Backpatch-through: 13 --- contrib/lo/sql/lo.sql | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'contrib/lo/sql') diff --git a/contrib/lo/sql/lo.sql b/contrib/lo/sql/lo.sql index 77039509245..99c3bd1fab3 100644 --- a/contrib/lo/sql/lo.sql +++ b/contrib/lo/sql/lo.sql @@ -27,4 +27,44 @@ DELETE FROM image; SELECT lo_get(43214); +-- Now let's try it with an AFTER trigger + +DROP TRIGGER t_raster ON image; + +CREATE CONSTRAINT TRIGGER t_raster AFTER UPDATE OR DELETE ON image + DEFERRABLE INITIALLY DEFERRED + FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster); + +SELECT lo_create(43223); +SELECT lo_create(43224); +SELECT lo_create(43225); + +INSERT INTO image (title, raster) VALUES ('beautiful image', 43223); + +SELECT lo_get(43223); + +UPDATE image SET raster = 43224 WHERE title = 'beautiful image'; + +SELECT lo_get(43223); -- gone +SELECT lo_get(43224); + +-- test updating of unrelated column +UPDATE image SET title = 'beautiful picture' WHERE title = 'beautiful image'; + +SELECT lo_get(43224); + +-- this case used to be buggy +BEGIN; +UPDATE image SET title = 'beautiful image' WHERE title = 'beautiful picture'; +UPDATE image SET raster = 43225 WHERE title = 'beautiful image'; +SELECT lo_get(43224); +COMMIT; + +SELECT lo_get(43224); -- gone +SELECT lo_get(43225); + +DELETE FROM image; + +SELECT lo_get(43225); -- gone + DROP TABLE image; -- cgit v1.2.3