Horton

Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>, Noah Misch <noah@leadboat.com>
Date: 2024-07-22T22:36:34Z
Lists: pgsql-hackers

Commits

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  1. Test that vacuum removes tuples older than OldestXmin

  2. Lower minimum maintenance_work_mem to 64kB

  3. Add accidentally omitted test to meson build file

  4. Use DELETE instead of UPDATE to speed up vacuum test

  5. Revert "Test that vacuum removes tuples older than OldestXmin"

  6. Ensure vacuum removes all visibly dead tuples older than OldestXmin

Melanie Plageman <melanieplageman@gmail.com> writes:
> We've only run tests with this commit on some of the back branches for
> some of these animals. Of those, I don't see any failures so far. So,
> it seems the test instability is just related to trying to get
> multiple passes of index vacuuming reliably with TIDStore.

> AFAICT, all the 32bit machine failures are timeouts waiting for the
> standby to catch up (mamba, gull, merswine). Unfortunately, the
> failures on copperhead (a 64 bit machine) are because we don't
> actually succeed in triggering a second vacuum pass. This would not be
> fixed by a longer timeout.

Ouch.  This seems to me to raise the importance of getting a better
way to test multiple-index-vacuum-passes.  Peter argued upthread
that we don't need a better way, but I don't see how that argument
holds water if copperhead was not reaching it despite being 64-bit.
(Did you figure out exactly why it doesn't reach the code?)

> Because of this, I'm inclined to revert the test on 17 and master to
> avoid distracting folks committing other work and seeing those animals
> go red.

Agreed as a short-term measure.

			regards, tom lane