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Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com>

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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Antonin Houska <ah@cybertec.at>, Amit Kapila <amit.kapila16@gmail.com>, 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: 2026-04-14T16:55:17Z
Lists: pgsql-hackers 
Hello!

On Tue, Apr 14, 2026 at 3:58 PM Andres Freund <andres@anarazel.de> wrote:
> I still think this needs to be in the deadlock detector.  The lock cycle just
> needs to be a bit more complicated for a hack in JoinWaitQueue not to work.
> There's no guarantee that the wait that triggers the deadlock is actually on
> the relation being repacked.

I have started prototyping a way to declare a "future" lock which the
deadlock detector treats as a hard edge.
But I currently stuck on issues related to the fact that SUE doesn't
force weak locks (fast-path) to go through
FastPathTransferRelationLocks, so the deadlock detector can't handle
the case when another backend tries to execute LOCK TABLE repack_test
IN SHARE UPDATE EXCLUSIVE MODE;
Also, VACUUM takes the same lock.

I'm not sure how to deal with this in a non-hacky way. One option is
to force SUE to transfer locks if relation it is trying to lock
relation which marked with "future lock". But I am not sure it is good
enough or covers all tricky cases (multiple backends in the loop).

Best regards,
Mikhail.

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