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Re: Adding REPACK [concurrently]

Srinath Reddy Sadipiralla <srinath2133@gmail.com>

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From: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
To: Antonin Houska <ah@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Amit Kapila <amit.kapila16@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: 2026-04-02T00:19:42Z
Lists: pgsql-hackers 
Hi Antonin,

On Wed, Apr 1, 2026 at 10:36 PM Antonin Houska <ah@cybertec.at> wrote:

> Srinath Reddy Sadipiralla <srinath2133@gmail.com> wrote:
>
> > i was fuzz testing v48 , and found a crash when REPACK (concurrently)
> itself errors out,
> > 1) while running
> >
> > create table test(id int);
> > REPACK (concurrently) test;
> >
> > TBH i didn't knew this, sometimes it's better to not know "rules" ;)
> > [NOTE: maybe we should add that we can't run
> > REPACK (concurrently) on table without identity index or primary key
> into repack.sgml]
> >
> > ERROR:  cannot process relation "test"
> > 2026-04-01 19:06:31.211 IST [2495575] HINT:  Relation "test" has no
> identity index.
> > 2026-04-01 19:06:31.211 IST [2495575] STATEMENT:  repack (concurrently)
> test;
> > TRAP: failed Assert("proc->statusFlags ==
> ProcGlobal->statusFlags[proc->pgxactoff]"), File: "procarray.c", Line: 719,
> PID: 2495575
> > Here's the diff to solve this crash.
>
> Thanks. Attached here is v48-0006 fixed.
>

On Wed, Apr 1, 2026 at 8:25 PM Srinath Reddy Sadipiralla <
srinath2133@gmail.com> wrote:

> Here's the diff to solve this crash.



diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c
> index 29ba49744eb..d44092a407a 100644
> --- a/src/backend/commands/repack.c
> +++ b/src/backend/commands/repack.c
> @@ -284,7 +284,23 @@ ExecRepack(ParseState *pstate, RepackStmt *stmt, bool
> isTopLevel)
>   * that others can conflict with.
>   */
>   if ((params.options & CLUOPT_CONCURRENT) != 0)
> + {
> + /*
> + * Do not let other backends wait for our completion during their
> + * setup of logical replication. Unlike logical replication publisher,
> + * we will have XID assigned, so the other backends - whether
> + * walsenders involved in logical replication or regular backends
> + * executing also REPACK (CONCURRENTLY) - would have to wait for our
> + * completion before they can build their initial snapshot. It is o.k.

+ * for any decoding backend to ignore us because we do not change
> + * tuple descriptor of any table, and the data changes we write should
> + * not be decoded by other backends.
> + */
> + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
>   MyProc->statusFlags |= PROC_IN_CONCURRENT_REPACK;
> + ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
> + LWLockRelease(ProcArrayLock);
> + }
>
>   /*
>   * If a single relation is specified, process it and we're done ... unless
> @@ -988,22 +1004,6 @@ rebuild_relation(Relation OldHeap, Relation index,
> bool verbose,
>
>   if (concurrent)
>   {
> - /*
> - * Do not let other backends wait for our completion during their
> - * setup of logical replication. Unlike logical replication publisher,
> - * we will have XID assigned, so the other backends - whether
> - * walsenders involved in logical replication or regular backends
> - * executing also REPACK (CONCURRENTLY) - would have to wait for our
> - * completion before they can build their initial snapshot. It is o.k.
> - * for any decoding backend to ignore us because we do not change
> - * tuple descriptor of any table, and the data changes we write should
> - * not be decoded by other backends.
> - */
> - LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
> - MyProc->statusFlags |= PROC_IN_CONCURRENT_REPACK;
> - ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
> - LWLockRelease(ProcArrayLock);
> -
>   /*
>   * The worker needs to be member of the locking group we're the leader
>   * of. We ought to become the leader before the worker starts. The


i think as i did earlier in the diff, shouldn't we remove the duplicate code
from rebuild_relation, am i missing something?


-- 
Thanks,
Srinath Reddy Sadipiralla
EDB: https://www.enterprisedb.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