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/3496294.1737501...@sss.pgh.pa.us Backpatch-through: 13 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/ea68ea6320ff84f55cf30dff1af662fc0bf5dafa Modified Files -------------- contrib/lo/expected/lo.out | 69 ++++++++++++++++++++++++++++++++++++++++++ contrib/lo/sql/lo.sql | 41 +++++++++++++++++++++++++ src/backend/commands/trigger.c | 18 +++++------ 3 files changed, 118 insertions(+), 10 deletions(-)
