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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: 2026-01-28T02:06:00Z
Lists: pgsql-hackers 
Hello!

> PROC_IN_VACUUM shouldn't be used for the same reason
StartupDecodingContext()
>  avoids setting PROC_IN_LOGICAL_DECODING in transaction. I've removed
that and
>  the tests work for me. Especially the "cache lookup failed" error is
almost
>  certainly related. Please let me know if you still get the other errors

Yes, now it is passing.

>  (Except for 2, which is probably due to the MVCC-unsafe behavior, as
discussed
>  earlier.)

Not happening too. BTW, it was non MVCC-related, because in that case
relcheckxmin would catch it.

What if:

1) add new PROC_IN_REPACK flag
2) use it in catalog horizon, but not in data (like was done in [0] for
PROC_IN_SAFE_IC)

And after we have options:
    3) do not "table_close(NewHeap, NoLock);" -
keep ShareUpdateExclusiveLock all the time to prevent VACUUM enter
    4) do not heap_page_prune_opt in repack transaction (just using simple
flag)
Or
    3) preserve xmin/xmax of original transaction in repacked data
    4) but better to keep ShareUpdateExclusiveLock anyway

Seems to be enough.

> The 0006 part needs more work (definitely beyond PG 19).

This is sad, because if you are in a situation then you need REPACK -
pinning the horizon for too long may just finish your DB....
And also, even with 0006 we still need to build indexes, which might pin it
for long (even duration caused by a single index).

Mikhail.

[0]:
https://github.com/postgres/postgres/commit/d9d076222f5b94a85e0e318339cfc44b8f26022d

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