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Re: Adding REPACK [concurrently]

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

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From: Álvaro Herrera <alvherre@alvh.no-ip.org>
To: Antonin Houska <ah@cybertec.at>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-02-26T12:19:25Z
Lists: pgsql-hackers 
On 2026-Feb-25, Antonin Houska wrote:

> Srinath Reddy Sadipiralla <srinath2133@gmail.com> wrote:

> > 2) transient table's WALs - these are generated because of
> > concurrent changes done while applying the logical decoded changes
> > on the new transient table, i think this won't be a problem until
> > they only will get recycled but if they get archived , they are of
> > no use instead they consume more space and time during the archival
> > process.
> 
> VACUUM FULL / CLUSTER also produces (a lot of) WAL, so IMO there's
> nothing specific about REPACK.

Yeah, I don't think there's anything we can (or should) do about this.
It's just writing to the common WAL stream, which means that any
non-repack concurrent load is going to be producing WAL messages
interspersed with what is being done for repack.  So it's not possible
to skip archiving those files, or anything of the sort.


In fact, these messages being written to WAL is how REPACK is going to
be transmitted to replicas.

(Actually, now that I think about this, I realize that I don't know how
this part really works, and I should.  Back to code review it is then.)

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"At least to kernel hackers, who really are human, despite occasional
rumors to the contrary" (LWN.net)

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