Horton

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

Robert Haas <robertmhaas@gmail.com>

View thread
From: Robert Haas <robertmhaas@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Peter Geoghegan <pg@bowt.ie>, Pg Hackers <pgsql-hackers@postgresql.org>, Noah Misch <noah@leadboat.com>
Date: 2024-06-25T23:33:35Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  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

On Tue, Jun 25, 2024 at 4:41 PM Andres Freund <andres@anarazel.de> wrote:
> I doubt that's doable in the back branches. And even on HEAD, I don't think
> it's a particularly attractive option - there's just a global vistest for each
> of the types of objects with a specific horizon (they need to be updated
> occasionally, e.g. when taking snapshots). So there's not really a spot to put
> an associated OldestXmin. We could put it there and remove it at the end of
> vacuum / in an exception handler, but that seems substantially worse.

Oh, right: I forgot that the visibility test objects were just
pointers to global variables.

Well, I don't know. I guess that doesn't leave any real options but to
fix it as Melanie proposed. But I still don't like it very much. I
feel like having to test against two different thresholds in the
pruning code is surely a sign that we're doing something wrong.

-- 
Robert Haas
EDB: http://www.enterprisedb.com