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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Alexander Lakhin <exclusion@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Amit Kapila <amit.kapila16@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-04-10T10:57:47Z
Lists: pgsql-hackers

Attachments

Alexander Lakhin <exclusion@gmail.com> wrote:

> Could you please look at an assertion failure produced by the following
> script, starting from 0d3dba38c:?
> createdb db1
> createdb db2
> 
> echo "
> CREATE TABLE t0 (a text);
> BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
> INSERT INTO t0 VALUES ('a');
> SELECT pg_sleep(1);
> " | psql db1 &
> 
> echo "
> CREATE TABLE t1 (id int PRIMARY KEY);
> CREATE TABLE t2 (id int PRIMARY KEY, a TEXT, FOREIGN KEY (id) REFERENCES t1);
> SET min_parallel_table_scan_size = 1;
> REPACK (CONCURRENTLY) t2;
> " | psql db2
> wait
> 
> It triggers for me:
> TRAP: failed Assert("TransactionIdPrecedesOrEquals(TransactionXmin, RecentXmin)"), File: "procarray.c", Line: 2071, PID: 3529520

Attached is a fix that works for me.

Nevertheless, REPACK (CONCURRENTLY) in your test goes ahead only due to commit
0d3dba38c7, which will probably be reverted [1]. Then REPACK will wait for the
transaction in the other database (db1) to complete before it can actually
start.

Thanks for the report!

[1] https://www.postgresql.org/message-id/cdgw4sbbfcgk6du3iv54r2dgiy4tfywoklbotlmj4irxavdcr3@glxfw5jj277q

-- 
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