Re: Adding REPACK [concurrently]

Jim Jones <jim.jones@uni-muenster.de>

From: Jim Jones <jim.jones@uni-muenster.de>
To: Antonin Houska <ah@cybertec.at>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Cc: alvherre@alvh.no-ip.org, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-03-23T16:07:24Z
Lists: pgsql-hackers

Attachments

Hi,

while reviewing another patch I noticed that REPACK is trying to access
temp tables from other sessions.

== session 1 ==

$ psql postgres
psql (19devel)
Type "help" for help.

postgres=# SELECT pg_backend_pid();
 pg_backend_pid
----------------
         730392
(1 row)

postgres=# CREATE TEMP TABLE tmp AS SELECT generate_series(1, 1000) AS id;
SELECT 1000
postgres=# BEGIN;
LOCK TABLE tmp IN SHARE MODE;
BEGIN
LOCK TABLE
postgres=*#

== session 2 ==

$ psql postgres
psql (19devel)
Type "help" for help.

postgres=# REPACK;
(waits for LOCK)

== session 3 ==

$ psql postgres
psql (19devel)
Type "help" for help.

postgres=# SELECT pid, relation::regclass, mode, granted
FROM pg_locks
WHERE relation::regclass::text ~~ '%.tmp%';
  pid   |    relation    |        mode         | granted
--------+----------------+---------------------+---------
 730608 | pg_temp_12.tmp | AccessExclusiveLock | f
 730392 | pg_temp_12.tmp | ShareLock           | t
(2 rows)

The same applies for REPACK USING INDEX if indisclustered is true.

I played a bit with the code and perhaps skipping temp relations in
get_tables_to_repack() before they're added to the list can do the
trick. I tried the draft attached and REPACK could run despite the LOCK
in the other session... in case it helps.


Best, Jim

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