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Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com>

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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
To: Antonin Houska <ah@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-02-02T10:04:45Z
Lists: pgsql-hackers 
Hello!


> I think it *is* related. My earlier patch version, which used the
> PROC_IN_VACUUM flag improperly [1] was also causing visibility issues.
Please
> let me know if you manage to reproduce the issue with v32.

Will try. Just to highlight - first error happened on v31 *without*
PROC_IN_REPACK.
Second error had PROC_IN_REPACK code, but it wasn't executed (flag wasn't
set) - that's why I think it is not related.

> I'm confused by hearing a complaint about complexity of code that I
haven't
> posted yet. And I don't understand the relationship to "replication
logic":
> REPACK (CONCURRENTLY) tries to avoid decoding of data changes in the *new*
> (transient) relation anyway.

I am not about complexity of code, but more about complexity of approach
(introducing new things like cache-only relations).
"Replication logic" - is about the fact you mentioned that such a relation
is going to be replicated to standby (as result, some replication-related
code is affected too, probably standby promotion also).

Compared to the PROC_IN_REPACK flag - it feels overly complicated for me.
PROC_IN_REPACK is the simplest thing here - just exclude XID from
data-horizon, but keep it in catalog. That's all.

Also, maybe I sound a little bit rude, sorry, it is just because of the
language barrier.

> 3) XID assigned early due to creation of catalog entries for the new
table -
> that XID prevents the VACUUM xmin horizon from advancing till the end of
the
> transaction, i.e. till the end of REPACK execution.

Yes, but PROC_IN_REPACK covers it as well. That xid only in the catalog
horizon.

> IMO it's better for users to see the correct data than ERROR. But it still
> needs work.
Agreed, for me it is ordered like this (from bad to good):

1) silently see incorrect data in rear race
2) receive error instead in that race    <----- acceptable for me
3) no error, data is correct

Best regards,
Mikhail.

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