Horton

Re: New strategies for freezing, advancing relfrozenxid early

Nikita Malakhov <hukutoc@gmail.com>

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From: Nikita Malakhov <hukutoc@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Peter Geoghegan <pg@bowt.ie>, Matthias van de Meent <boekewurm+postgres@gmail.com>, John Naylor <john.naylor@enterprisedb.com>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-12-20T18:04:14Z
Lists: pgsql-hackers 
Hi!

I'll try to apply this patch onto my branch with Pluggable TOAST to test
these mechanics with new TOAST. Would reply on the result. It could
be difficult though, because both have a lot of changes that affect
the same code.

>I'm not sure how much this would help with bloat. I suspect that it
>could make a big difference with the right workload. If you always
>need frequent autovacuums, just to deal with bloat, then there is
>never a good time to run an aggressive antiwraparound autovacuum. An
>aggressive AV will probably end up taking much longer than the typical
>autovacuum that deals with bloat. While the aggressive AV will remove
>as much bloat as any other AV, in theory, that might not help much. If
>the aggressive AV takes as long as (say) 5 regular autovacuums would
>have taken, and if you really needed those 5 separate autovacuums to
>run, just to deal with the bloat, then that's a real problem.  The
>aggressive AV effectively causes bloat with such a workload.



On Tue, Dec 20, 2022 at 12:01 PM Jeff Davis <pgsql@j-davis.com> wrote:

> On Sun, 2022-12-18 at 14:20 -0800, Peter Geoghegan wrote:
> > Attached is v10, which fixes this issue, but using a different
> > approach to the one I sketched here.
>
> In 0001, it's fairly straightforward rearrangement and looks like an
> improvement to me. I have a few complaints, but they are about pre-
> existing code that you moved around, and I like that you didn't
> editorialize too much while just moving code around. +1 from me.
>
>
> --
> Jeff Davis
> PostgreSQL Contributor Team - AWS
>
>
>
>
>

-- 
Regards,

--
Nikita Malakhov
Postgres Professional
https://postgrespro.ru/

Commits

  1. Revert "Add eager and lazy freezing strategies to VACUUM."

  2. Add eager and lazy freezing strategies to VACUUM.

  3. Refine the definition of page-level freezing.

  4. Avoid special XID snapshotConflictHorizon values.

  5. Add page-level freezing to VACUUM.

  6. Remove overzealous MultiXact freeze assertion.

  7. Refactor how VACUUM passes around its XID cutoffs.

  8. Deduplicate freeze plans in freeze WAL records.

  9. Set relfrozenxid to oldest extant XID seen by VACUUM.

  10. Only skip pages marked as clean in the visibility map, if the last 32

  11. Add vacuum_freeze_table_age GUC option, to control when VACUUM should