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Re: Adding REPACK [concurrently]

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Antonin Houska <ah@cybertec.at>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, 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: 2026-04-01T12:35:01Z
Lists: pgsql-hackers 
On Wed, Apr 1, 2026 at 5:12 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> On 2026-Apr-01, Amit Kapila wrote:
>
> > BTW, is the reason to skip REPACK while building a snapshot is that it
> > can take a long time to finish?
>
> As I understand the issue, yes, that's precisely the problem: if you
> have one REPACK running, then starting a second REPACK (which requires
> building a new snapshot) would have to wait until the first REPACK is
> over.  In other words, you wouldn't be able to have two repacks running
> concurrently.  This sounds like a problematic requirement.  So having
> snapbuild ignore REPACK is there to allow the second REPACK to work at
> all.  But more generally,  *all* users of snapbuild would be prevented
> from starting until REPACK is done; so if you have a very very large
> table that takes a long time to repack, then everything would be blocked
> behind it until it completes, which sounds extremely unpleasant.
>
> So, if we're unable to get this particular patch in, we would have to
> have a big fat warning in the docs, telling people to be careful about
> other load if they choose to run concurrent repack -- it could have
> serious consequences.
>

Right, I think during this time logical workers will keep timing out
and restarting without any progress because during this wait, we won't
be sending keep_alive messages.

-- 
With Regards,
Amit Kapila.

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