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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Mihail Nikalayeu <mihailnikalayeu@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-03-13T08:11:38Z
Lists: pgsql-hackers 
Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> I offer the following rather trivial fixup diffs, which I think should
> be mostly be for 0002.

Thanks, just a few comments:

* 0002 - I didn't add the 'repack_' prefix because the function is static, but
  realize now that it might be useful from the code browsing perspective.

* 0008 - It's possible during query execution, when you know exactly which
  attributes you need to fetch from the tuple. However in store_change(), we
  don't know which attributes are external (indirect) without deforming them
  all.

> Other trivial things I'd like to change, if you don't mind,

> - the name pgoutput_repack sounds wrong to me.  I would rather say
>   rpck_output, repack_output, repack_plugin, ... or something.  I don't
>   understand where the suffix "output" comes from in the name
>   "pgoutput", but it sounds like arbitrary nonsense to me.

No strong preference here, except that I don't like "rpck_...". How about
pgoutput/repack.c? I think I tried to put the plugin into the existing
"pgoutput" directory at some point, but don't remember why I eventually
rejected that approach.

> - I would rename the routines in that file to also have the name
>   "repack", probably as prefixes.

ok

> One thing we need and is rather not trivial, is to go through the table
> AM interface rather than calling heapam.c routines directly.  I'm
> working on this now and will present a patch later.

It occurred to me too, at least because copy_table_data() calls
table_relation_copy_for_cluster() rather than
heapam_relation_copy_for_cluster(). Thanks for working on it.

> Another thing I noticed while going over the code was that we seem to
> spill whole tuples even for things like the old tuple of an UPDATE and
> for DELETE, but unless I misunderstand how this works, these shouldn't
> be necessary: we just need the replica identity so that we can locate
> the tuple to operate on.  Especially for tuples that contain large
> toasted attributes, this is likely important.

I think we don't need to care, as both heap_update() and heap_delete() call
ExtractReplicaIdentity(). That returns a real tuple, but it only contains the
attributes constituting the replica identity. The other ones are set to
NULL.

> It may make sense to use the TupleTableSlot interface rather than
> HeapTuple for everything.  I'm not really sure about this though.

Isn't this part of the adoption of table AM? For example, table_tuple_insert()
accepts tuple slot rather than heap tuple.

-- 
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