Horton

Re: pgsql: Update guidance for running vacuumdb after pg_upgrade.

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Christoph Berg <myon@debian.org>
Cc: Corey Huinker <corey.huinker@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-04-22T21:29:21Z
Lists: pgsql-hackers

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On Tue, Apr 22, 2025 at 11:03:29PM +0200, Christoph Berg wrote:
> Re: Nathan Bossart
>> In any case, IMO it's unfortunate
>> that we might end up recommending roughly the same post-upgrade steps as
>> before even though the optimizer statistics are carried over.
> 
> Maybe the docs (and the pg_upgrade scripts) should recommend the old
> procedure by default until this gap is closed? People could then still
> opt to use the new procedure in specific cases.

I think we'd still want to modify the --analyze-in-stages recommendation
(from what is currently recommended for supported versions).  If we don't,
you'll wipe out the optimizer stats you brought over from the old version.

Here is a rough draft of what I am thinking.

-- 
nathan

Commits

  1. Further adjust guidance for running vacuumdb after pg_upgrade.

  2. vacuumdb: Don't skip empty relations in --missing-stats-only mode.

  3. Update guidance for running vacuumdb after pg_upgrade.

  4. Redefine pg_class.reltuples to be -1 before the first VACUUM or ANALYZE.