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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-01-05T10:54:07Z
Lists: pgsql-hackers 
Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> Hello!
> 
> On Sat, Dec 13, 2025 at 7:45 PM Mihail Nikalayeu
> <mihailnikalayeu@gmail.com> wrote:
> > Stress tests for REPACK concurrently in attachment.
> 
> To run:
> ninja && meson test --suite setup && meson test --print-errorlogs
> --suite amcheck *007*
> ninja && meson test --suite setup && meson test --print-errorlogs
> --suite amcheck *008*

Thanks for running the tests!

> Results for v28:
> 
> Up to " v28-0005-Use-background-worker-to-do-logical-decoding.patch":
> 
> Technically it passes, but sometimes I saw 0% CPU usage for long
> periods with such stacks (looks like it happens for 0008 more often):

...

> Probably it is because
> > 100000L,    /* XXX Tune the delay. */
> 
> 100 seconds is clearly too much.

I confused milliseconds with microseconds. Since I was only running the code
with debugger, the long delays didn't appear to be a problem.

Instead of tuning the timeout, I'm thinking of introducing a condition
variable that signals WAL flushing.

> For "v28-0006-Use-multiple-snapshots-to-copy-the-data.patch":
> 
> 0007: crash with
> 
> TRAP: failed Assert("portal->portalSnapshot == GetActiveSnapshot()"),
> File: "../src/backend/tcop/pquery.c", Line: 1169, PID: 178414

Thanks. I'll check when I have time for this part.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.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