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Re: Adding REPACK [concurrently]

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Antonin Houska <ah@cybertec.at>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-04-06T10:48:23Z
Lists: pgsql-hackers 
On 2026-Apr-06, Mihail Nikalayeu wrote:

> repack.c:2725
> 
>     if (!VARATT_IS_EXTERNAL(varlen))
>           continue;
> 
> I think it should be VARATT_IS_EXTERNAL_INDIRECT - the same as in pgrepack:244.

Right.

> Also,  after
> 
> natt_ext--;
> 
> I think it worth to add
> 
> Assert(natt_ext >= 0);
> 
> or Assert(natt_ext == 0); but in another place.
> 
> Or exit early with
>      for (int i = 0; i < desc->natts && natt_ext > 0; i++)

Hmm, how about something like this?

            natt_ext--;
            if (natt_ext < 0)
                ereport(ERROR,
                        errcode(ERRCODE_DATA_CORRUPTED),
                        errmsg("insufficient number of attributes stored separately"));

I'd like to give more details, such as the tuple's identity, but that
seems hard ...

> ----------------------------
> repack.c:2587
> 
>     table_tuple_insert(rel, slot, GetCurrentCommandId(true),
>        HEAP_INSERT_NO_LOGICAL, NULL);
> 
> More idiomatic to use TABLE_INSERT_NO_LOGICAL instead.

Ah right.

> ----------------------------
> repack.c:2696
> 
>      ExecForceStoreHeapTuple(tup, slot, false);
> 
> AFAIU there is a memory leak here. Memory allocated above (for tuple)
> is not freed in any way, because shouldFree == false.
> Also, ExecClearTuple (tts_virtual_clear for virtual tuples) requires
> TTS_SHOULDFREE to be set to free anything.

Yeah but I don't want the virtual tuple to be materialized (which would
happen in tts_virtual_materialize if I set shouldFree=true).  The memory
should be freed in 
		ResetPerTupleExprContext(chgcxt->cc_estate);
anyway, right?  Maybe deserves a comment.

> -------------------------
> grab ShareUpdateExclusiveLock (jsut like VACUUM
> 
> typo in "just"

Right.

> --------------------------
> 
> "If the identity index is not set due to replica identity being, PK"
> 
> Missing "FULL" after "being"?

Ah yeah, I rewrote this.

> -------------------------
> 
> Commit message:
> 
> "intial copy" -> "initial copy"
> "backed performing REPACK" -> "backend performing REPACK"

Thanks!

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Sallah, I said NO camels! That's FIVE camels; can't you count?"
(Indiana Jones)

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