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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: Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-04-09T09:26:29Z
Lists: pgsql-hackers 
Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> On Thu, Apr 9, 2026 at 10:43 AM Antonin Houska <ah@cybertec.at> wrote:
> > This approach LGTM when it comes to concurrent DDLs. However, consider REPACK
> > holding ShareUpdateExclusiveLock (SUEL) and VACUUM (w/o VACOPT_SKIP_LOCKED)
> > waiting for the same lock. Once REPACK releases its SUEL, VACUUM gets it and
> > processes the table, then REPACK finally gets AccessExclusiveLock (AEL) and
> > finishes too.
> 
> > One more thing we may prevent from sneaking into that hole is a
> > VACUUM. It will not break anything, but will be huge waste of time and
> > resources.
> 
> 
> I thought about that too, I think we may just add some kind of
> CheckTableNotInUse in VACUUM after getting the SUEL.

Sure, it's possible, but IMO the principal question is whether REPACK should
let VACUUM and DDLs error out, or just let them wait.

-- 
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