Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com>

From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>

To: Antonin Houska <ah@cybertec.at>

Cc: Andres Freund <andres@anarazel.de>, Amit Kapila <amit.kapila16@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>

Date: 2026-04-26T13:34:00Z

Lists: pgsql-hackers

Attachments

nocfbot-v2-0001-Protect-concurrent-repack-lock-upgrades.patch (application/octet-stream) patch v2-0001

Hello!

I think I have a good enough approach now (at least balancing
complexity and outcome).

Patch (and commit message) is quite explanatory, but in a few words:

- add 'upgradeIntent' to PROCLOCK (set by REPACK)
- check that in the deadlock detector. If the backend finds the cycle
and is part of it, but because it's upgrading an already announced
lock, it cancels another backend instead of itself.
- use that in the fast path of simple deadlock detection to avoid
pointless waiting (for the easy case involving two backends)

It doesn't cover all scenarios (explained in patch details) but for
majority of realistic scenarios - yes.
It may be extended to cover all of them, but I'm not sure it's worth
the additional complexity.

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 →

Allow old WAL recycling during REPACK CONCURRENTLY
- 45b02984e2fa 19 (unreleased) landed
Advance restart_lsn more eagerly in LogicalConfirmReceivedLocation
- 38470c2c1ea7 19 (unreleased) landed
Remove unnecessary signal handler change
- 5d48d3b14e0e 19 (unreleased) landed
Improve REPACK (CONCURRENTLY) error messages some more
- 378dffaf8c80 19 (unreleased) landed
Revert "Allow logical replication snapshots to be database-specific"
- 01a80f062146 19 (unreleased) landed
Move REPACK (CONCURRENTLY) test out of stock regression tests
- 4b2aa4b39cba 19 (unreleased) landed
REPACK: do not require REPLICATION or LOGIN
- 5dbb63fc82b7 19 (unreleased) landed
Add missing initialization
- 05c401d5786a 19 (unreleased) landed
Simplify declaration of memcpy target
- 2cff363715ef 19 (unreleased) landed
Reserve replication slots specifically for REPACK
- e76d8c749c31 19 (unreleased) landed
doc: Add an example of REPACK (CONCURRENTLY)
- 8fb95a8ab6e5 19 (unreleased) landed
Allow logical replication snapshots to be database-specific
- 0d3dba38c777 19 (unreleased) landed
Avoid different-size pointer-to-integer cast
- a3b069ef90bd 19 (unreleased) landed
Fix valgrind failure
- 5bcc3fbd196c 19 (unreleased) landed
Add CONCURRENTLY option to REPACK
- 28d534e2ae0a 19 (unreleased) landed
Rename cluster.c to repack.c (and corresponding .h)
- c0b53ec06309 19 (unreleased) landed
Allow index_create to suppress index_build progress reporting
- caec9d9fadf1 19 (unreleased) landed
Make index_concurrently_create_copy more general
- 33bf7318f94c 19 (unreleased) landed
Document the 'command' column of pg_stat_progress_repack
- a630ac5c2016 19 (unreleased) landed
Introduce the REPACK command
- ac58465e0618 19 (unreleased) landed
Toggle logical decoding dynamically based on logical slot presence.
- 67c20979ce72 19 (unreleased) cited
Split vacuumdb to create vacuuming.c/h
- c4067383cb2c 19 (unreleased) landed
Remove ReorderBufferTupleBuf structure.
- 08e6344fd642 17.0 cited
Revert changes to CONCURRENTLY that "sped up" Xmin advance
- 042b584c7f7d 14.4 cited
VACUUM: ignore indexing operations with CONCURRENTLY
- d9d076222f5b 14.0 cited