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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Srinath Reddy Sadipiralla <srinath2133@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Noah Misch <noah@leadboat.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, vignesh C <vignesh21@gmail.com>, 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: 2026-04-07T08:57:46Z
Lists: pgsql-hackers 
Srinath Reddy Sadipiralla <srinath2133@gmail.com> wrote:

> Hi Tom,
> 
> On Tue, Apr 7, 2026 at 10:14 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
>  Maybe you saw this already, but BF member skink is failing on
>  src/test/modules/injection_points/specs/repack.spec:
> 
>  https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-04-06%2022%3A50%3A41
> 
> i looked into this , it seems like valgrind catches the uninitialised padding bytes, which
> repack worker is writing using BufFileWrite, it seems this fix solved the problem.
> 
> diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
> index 2e6197f5f35..f5682b87626 100644
> --- a/src/backend/utils/time/snapmgr.c
> +++ b/src/backend/utils/time/snapmgr.c
> @@ -1739,6 +1739,8 @@ SerializeSnapshot(Snapshot snapshot, char *start_address)
>  
>   Assert(snapshot->subxcnt >= 0);
>  
> + MemSet(&serialized_snapshot, 0, sizeof(SerializedSnapshotData));
> +
>   /* Copy all required fields */
>   serialized_snapshot.xmin = snapshot->xmin;
>   serialized_snapshot.xmax = snapshot->xmax;
> 
> thoughts?

Could you reproduce the failure in your environment?

I haven't thought of this explanation because BufFileWrite() only copies the
data to a buffer in the BufFile structure and BufFileDumpBuffer() writes the
buffer. Maybe valgrind is able to track the copying?

-- 
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