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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: Robert Treat <rob@xzilla.net>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Antonin Houska <ah@cybertec.at>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-03-16T16:03:47Z
Lists: pgsql-hackers 
On 2026-Mar-16, Robert Treat wrote:

> I'm never excited about adding GUCs, but at first thought this seems
> like a decent work-around; most people are unlikely to run multiple
> repack concurrently's, but they can if needed. (I think the most
> likely use case is on clusters using the "database per customer"
> pattern, but if we have the guc, people will have a means to deal with
> it).

I wonder if, longer term, it would make sense to do away with the
max_replication_slots GUC (and this new one) altogether, and use dynamic
shared memory for slots instead.  There's of course always the danger
that people would accumulate arbitrary numbers of slots since they would
never be forced to check.  But that may be a lesser problem than having
to gauge these GUCs with any care.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"You're _really_ hosed if the person doing the hiring doesn't understand
relational systems: you end up with a whole raft of programmers, none of
whom has had a Date with the clue stick."              (Andrew Sullivan)
https://postgr.es/m/20050809113420.GD2768@phlogiston.dyndns.org

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