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Re: Adding REPACK [concurrently]

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Matthias van de Meent <boekewurm+postgres@gmail.com>
Cc: Antonin Houska <ah@cybertec.at>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-03-16T15:10:46Z
Lists: pgsql-hackers 
On 2026-Mar-16, Matthias van de Meent wrote:

> Note that most of my argument hinges on the impact on other, unrelated
> databases/tables/sessions. Replication slots have a hard cap defined
> at startup, and effective_wal_level increases the WAL generated by
> practically all backends.

I'd rather have a new GUC to declare a bunch of additional slots that
are reserved exclusively for repack, set its default to something like
3, and call it a day.  If all repack slots are in use, you don't get to
run repack, period.

A slot costs nothing if unused, and we really don't want to make the
interaction with regular replication more complicated than it is today.

> However, we don't live in that world, so I am opposed to allowing
> table owners without REPLICATION to take any/all replication slots.

I think requiring REPACK users to have the REPLICATION priv is rather
user unfriendly.  Some potential REPACK users might not have any other
use for replication at all.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"World domination is proceeding according to plan"        (Andrew Morton)

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