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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: 2026-02-09T11:50:03Z
Lists: pgsql-hackers 
Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> > Indeed, the server log seems to indicate relationship to
> > VACUUM:
> > 2026-02-01 16:44:58.878 UTC autovacuum worker[22589] LOG:  automatic vacuum of table "postgres.pg_catalog.pg_class": index scans: 1
> 
> O, it's a good clue!
> 
> I have added some vacuum calls for pg_class in a stress test - and now it fails much more often (check attachment).
> 
> It is "ERROR:  cache lookup failed for relation" - but I think it may share the cause with "attempted to overwrite invisible tuple.

I've just reported one issue [1] that causes this, but that does not seem to
be related to the "attempted to overwrite invisible tuple" error.

> See:
> https://cirrus-ci.com/build/4852126532239360 - with "Use multiple snapshots to copy the data."
> https://cirrus-ci.com/build/6429084491710464 - with "Use background worker to do logical decoding."
> 
> But I am unable to reproduce the issue with only "Add CONCURRENTLY option to REPACK command."
> https://cirrus-ci.com/build/6467070524653568

No idea why VACUUM makes the issue happen too often. Maybe it's related to the
PD_ALL_VISIBLE flage, but I've got no detailed explanation. I also don't know
why it does not reproduce w/o the logical decoding worker.

Thanks again for your testing!

[1] https://www.postgresql.org/message-id/61812.1770637345%40localhost

-- 
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