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Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com>

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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Antonin Houska <ah@cybertec.at>, Andres Freund <andres@anarazel.de>, 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: 2026-06-17T20:10:22Z
Lists: pgsql-hackers 
Hello, Álvaro!

>  Right.  I spent some time looking at this patch just before pgconf.dev

Thanks!

> I have to admit I was a bit scared -- that code is really
> non-obvious, and breakage here could mean big trouble in case something
> goes wrong in weird situations.

Another option we may consider for pg19 - is just a simple
local-memory flag: "If I detect a deadlock and I am REPACK - cancel
another, not me".
It doesn't handle all tricky cases, but it deals with the most common
ones and is much easier and less invasive to implement.

It reuses mechanics that were already present (though unused, they
were documented as "for future" in comments).
POC of that approach is here - [0].

Best regards,
Mikhail.

[0]: https://www.postgresql.org/message-id/flat/CADzfLwURKVNQ++Dpi7bjoGfj-8pchDQEVex3eWBx0NCYn6TbDQ@mail.gmail.com#bceb18354aa20c130a94b1deedd76fb7

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