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Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Tomas Vondra <tomas@vondra.me>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, vignesh C <vignesh21@gmail.com>, Srinath Reddy Sadipiralla <srinath2133@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: 2026-04-08T10:46:46Z
Lists: pgsql-hackers 
Tomas Vondra <tomas@vondra.me> wrote:

> while building on a rpi5 with a 32-bit system, I'm getting these warnings:
> 
> config.status: linking src/makefiles/Makefile.linux to src/Makefile.port
> In file included from ../../../src/include/access/tupmacs.h:20,
>                  from ../../../src/include/access/htup_details.h:20,
>                  from ../../../src/include/access/relscan.h:17,
>                  from ../../../src/include/access/heapam.h:19,
>                  from repack.c:36:
> In function ‘VARSIZE_ANY’,
>     inlined from ‘restore_tuple’ at repack.c:2731:15:
> ../../../src/include/varatt.h:243:51: warning: array subscript
> ‘varattrib_4b[0]’ is partly outside array bounds of ‘union
> <anonymous>[1]’ [-Warray-bounds=]
>   243 |         ((((const varattrib_4b *) (PTR))->va_4byte.va_header >>
> 2) & 0x3FFFFFFF)
>       |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
> ../../../src/include/varatt.h:467:24: note: in expansion of macro
> ‘VARSIZE_4B’
>   467 |                 return VARSIZE_4B(PTR);
>       |                        ^~~~~~~~~~
> repack.c: In function ‘restore_tuple’:
> repack.c:2717:49: note: object ‘chunk_header’ of size 4
>  2717 |                         }                       chunk_header;
>       |                                                 ^~~~~~~~~~~~
> In function ‘VARSIZE_ANY’,
>     inlined from ‘restore_tuple’ at repack.c:2734:4:
> ../../../src/include/varatt.h:243:51: warning: array subscript
> ‘varattrib_4b[0]’ is partly outside array bounds of ‘union
> <anonymous>[1]’ [-Warray-bounds=]
>   243 |         ((((const varattrib_4b *) (PTR))->va_4byte.va_header >>
> 2) & 0x3FFFFFFF)
>       |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
> ../../../src/include/varatt.h:467:24: note: in expansion of macro
> ‘VARSIZE_4B’
>   467 |                 return VARSIZE_4B(PTR);
>       |                        ^~~~~~~~~~
> repack.c: In function ‘restore_tuple’:
> repack.c:2717:49: note: object ‘chunk_header’ of size 4
>  2717 |                         }                       chunk_header;
>       |                                                 ^~~~~~~~~~~~

> I'm not sure if it's just the compiler (gcc 14.2) being pesky, or if
> it's an actual issue. The repack tests seem to pass fine.

We already introduced this definition above in the function to suppress this
kind of warning

    union
    {
	    alignas(int32) varlena hdr;
	    char		data[sizeof(void *)];
    }			chunk_header;

The problem on a 32-bit system probably is that sizeof(void *) is 4. We need
some other constant. Maybe (sizeof(varlena) + 1) ...

Thanks.

-- 
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