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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: Andres Freund <andres@anarazel.de>
Cc: Noah Misch <noah@leadboat.com>, vignesh C <vignesh21@gmail.com>, Antonin Houska <ah@cybertec.at>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-04-06T21:59:59Z
Lists: pgsql-hackers 
On 2026-Apr-06, Andres Freund wrote:

> I just saw this got committed and wanted to briefly play with it.  It works
> nicely!

Yeah, I have to say that Antonin did a great job here.

> Except that at first I tried this in a debugging build, and was briefly rather
> dismayed by the performance.  It was really slow.  But it's not really related
> to repack / the patches here.
>
> In that config, the assert single-handled increases the time for a repack by
> 35% or so.

Yeah, I saw it was kinda sluggish, but wow, I didn't see *that* much
overhead.

> It's totally valid to not have done so initially, this is a quite complicated
> feature:
> 
> I saw this is using individual heap_insert()s during the
> heapam_relation_copy_for_cluster().  Doing individual WAL logged inserts isn't
> exactly cheap or efficient from a WAL volume perspective...
> 
> Is there anything other than round tuits preventing us from using
> multi_insert?
> 
> That actually would also reduce the cost in the REPACK decoding worker, due to
> having to parse far fewer WAL records.

Nope, not really ... but I don't have any :-(

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/

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