Horton

Re: New strategies for freezing, advancing relfrozenxid early

Peter Geoghegan <pg@bowt.ie>

View thread View on postgr.es
From: Peter Geoghegan <pg@bowt.ie>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: Jeff Davis <pgsql@j-davis.com>, 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: 2022-12-27T07:30:25Z
Lists: pgsql-hackers 
On Mon, Dec 26, 2022 at 10:57 PM Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
> I guessed that this assertion failure seemed to be caused by the commit 4ce3af[2],
> because the Assert() seemed to be added by the commit.

I agree that the problem is with this assertion, which is on the
master branch (not in recent versions of the patch series itself)
following commit 4ce3af:

else
{
    /*
    * Freeze plan for tuple "freezes xmax" in the strictest sense:
    * it'll leave nothing in xmax (neither an Xid nor a MultiXactId).
    */
    ....
    Assert(MultiXactIdPrecedes(xid, cutoffs->OldestMxact));
    ...
}

The problem is that FRM_INVALIDATE_XMAX multi processing can occur
both in Multis from before OldestMxact and Multis >= OldestMxact. The
latter case (the >= case) is far less common, but still quite
possible. Not sure how I missed that.

Anyway, this assertion is wrong, and simply needs to be removed.
Thanks for the report
-- 
Peter Geoghegan

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