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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-02-02T19:39:59Z
Lists: pgsql-hackers 
Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> > I think it *is* related. My earlier patch version, which used the
> > PROC_IN_VACUUM flag improperly [1] was also causing visibility issues.  Please
> > let me know if you manage to reproduce the issue with v32.
> 
> Will try. Just to highlight - first error happened on v31 *without* PROC_IN_REPACK.
> Second error had PROC_IN_REPACK code, but it wasn't executed (flag wasn't set) - that's why I think it is not related.

ok, v31 is the one that uses PROC_IN_VACUUM incorrectly.

> > I'm confused by hearing a complaint about complexity of code that I haven't
> > posted yet. And I don't understand the relationship to "replication logic":
> > REPACK (CONCURRENTLY) tries to avoid decoding of data changes in the *new*
> > (transient) relation anyway.
> 
> I am not about complexity of code, but more about complexity of approach (introducing new things like cache-only relations).
> "Replication logic" - is about the fact you mentioned that such a relation is going to be replicated to standby (as result, some
> replication-related code is affected too, probably standby promotion also).

I thought you mean logical replication. Regarding streaming replication, I
mentioned it rather for the record. I need to check details to see if it
requires special attention.

> Compared to the PROC_IN_REPACK flag - it feels overly complicated for me.
> PROC_IN_REPACK is the simplest thing here - just exclude XID from data-horizon, but keep it in catalog. That's all.

My preference is to avoid hacking procarray.c if a reasonable alternative
exists.

> Also, maybe I sound a little bit rude, sorry, it is just because of the language barrier.

No, that's fine. Since we've met at pgconf.eu, I think you're not a bad guy
:-) Technical discussions are mostly about problems, so they tend to sound
negative as such.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com

Commits

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

  1. Allow old WAL recycling during REPACK CONCURRENTLY

  2. Advance restart_lsn more eagerly in LogicalConfirmReceivedLocation

  3. Remove unnecessary signal handler change

  4. Improve REPACK (CONCURRENTLY) error messages some more

  5. Revert "Allow logical replication snapshots to be database-specific"

  6. Move REPACK (CONCURRENTLY) test out of stock regression tests

  7. REPACK: do not require REPLICATION or LOGIN

  8. Add missing initialization

  9. Simplify declaration of memcpy target

  10. Reserve replication slots specifically for REPACK

  11. doc: Add an example of REPACK (CONCURRENTLY)

  12. Allow logical replication snapshots to be database-specific

  13. Avoid different-size pointer-to-integer cast

  14. Fix valgrind failure

  15. Add CONCURRENTLY option to REPACK

  16. Rename cluster.c to repack.c (and corresponding .h)

  17. Allow index_create to suppress index_build progress reporting

  18. Make index_concurrently_create_copy more general

  19. Document the 'command' column of pg_stat_progress_repack

  20. Introduce the REPACK command

  21. Toggle logical decoding dynamically based on logical slot presence.

  22. Split vacuumdb to create vacuuming.c/h

  23. Remove ReorderBufferTupleBuf structure.

  24. Revert changes to CONCURRENTLY that "sped up" Xmin advance

  25. VACUUM: ignore indexing operations with CONCURRENTLY