postgres

History

Tom Lane a3179ab692 Recalculate where-needed data accurately after a join removal. Up to now, remove_rel_from_query() has done a pretty shoddy job of updating our where-needed bitmaps (per-Var attr_needed and per-PlaceHolderVar ph_needed relid sets). It removed direct mentions of the to-be-removed baserel and outer join, which is the minimum amount of effort needed to keep the data structures self-consistent. But it didn't account for the fact that the removed join ON clause probably mentioned Vars of other relations, and those Vars might now not be needed as high up in the join tree as before. It's easy to show cases where this results in failing to remove a lower outer join that could also have been removed. To fix, recalculate the where-needed bitmaps from scratch after each successful join removal. This sounds expensive, but it seems to add only negligible planner runtime. (We cheat a little bit by preserving "relation 0" entries in the bitmaps, allowing us to skip re-scanning the targetlist and HAVING qual.) The submitted test case drew attention because we had successfully optimized away the lower join prior to v16. I suspect that that's somewhat accidental and there are related cases that were never optimized before and now can be. I've not tried to come up with one, though. Perhaps we should back-patch this into v16 and v17 to repair the performance regression. However, since it took a year for anyone to notice the problem, it can't be affecting too many people. Let's let the patch bake awhile in HEAD, and see if we get more complaints. Per bug #18627 from Mikaël Gourlaouen. No back-patch for now. Discussion: https://postgr.es/m/18627-44f950eb6a8416c2@postgresql.org		1 year ago
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backend	Recalculate where-needed data accurately after a join removal.	1 year ago
bin	Reindent pg_verifybackup.c.	1 year ago
common	jsonapi: fix memory leakage during OOM error recovery.	1 year ago
fe_utils	pg_verifybackup: Verify tar-format backups.	1 year ago
include	Recalculate where-needed data accurately after a join removal.	1 year ago
interfaces	Add PQfullProtocolVersion() to surface the precise protocol version.	1 year ago
makefiles	Add -Wmissing-variable-declarations to the standard compilation flags	1 year ago
pl	Don't bother checking the result of SPI_connect[_ext] anymore.	1 year ago
port	Only perform pg_strong_random init when required	1 year ago
template	thread-safety: gmtime_r(), localtime_r()	1 year ago
test	Recalculate where-needed data accurately after a join removal.	1 year ago
timezone	…
tools	pg_verifybackup: Verify tar-format backups.	1 year ago
tutorial	…
.gitignore	…
DEVELOPERS	…
Makefile	…
Makefile.global.in	Add -Wmissing-variable-declarations to the standard compilation flags	1 year ago
Makefile.shlib	…
meson.build	…
nls-global.mk	…