Horton
Menu

Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

View thread
From: Antonin Houska <ah@cybertec.at>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-03-23T10:20:03Z
Lists: pgsql-hackers 
Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> On 2026-Mar-19, Antonin Houska wrote:
> 
> > Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> > 
> > > So here's v43.  Here, I've changed the CONCURRENTLY implementation to go
> > > through table AM.  This necessitated changing it to use tuples in slots
> > > instead of HeapTuple.  This is good because we can avoid repeated tuple
> > > form/deform, which could get pretty expensive.  Antonin's 0004 patch
> > > here looks suspicious here though, because it deforms the tuple and
> > > forms it again, which sounds unnecessary now.
> > 
> > I suppose you mean
> > v42-0004-Serialize-decoded-tuples-without-flattening.patch. This deforms the
> > tuple to get the external attributes and to write them to file. The tuple the
> > logical worker received from reorderbuffer.c cannot be passed to the backend
> > executing REPACK because it may contain "external indirect" attributes,
> > i.e. pointers to the worker's memory.
> 
> No, that patch has been absorbed in what is now v43-0003.  I meant
> v43-0004 "Use BulkInsertState when copying data to the new heap.",
> that's why I said "patch 0004 here".  In this patch, we have
> reform_tuple which deforms the tuple, sets to NULL any attribute that's
> marked dropped, and then forms a new one.  This is wasteful and should
> probably be done elsewhere, while the tuple is still in slot
> representation.  In fact, I suspect it may not be necessary at all
> anymore.

The idea to "reform" the tuple comes from VACUUM FULL / CLUSTER. I agree the
"deform" and "form" steps are no longer needed when we use tuple slots.

-- 
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