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Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com>

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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Antonin Houska <ah@cybertec.at>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-03-20T12:35:00Z
Lists: pgsql-hackers 
Hello, everyone!

Some comments for v43:

 ---
src/backend/commands/cluster.c:3211

slot_attisnull(dest, i) uses a 0-based loop index but slot_attisnull
starts with "Assert(attnum > 0);".
Also, it proves it has not been tested in any way yet.

------------------------------

src/backend/storage/ipc/standby.c:1376

"if (xlrec.xcnt > 0)"
looks like it should be "xlrec.xcnt + xlrec.xcnt_repack > 0" because
of "CurrentRunningXacts->xcnt = count - subcount - count_repack;"

------------------------------

src/backend/storage/ipc/procarray.c:2673-2681

"nrepack = logical_decoding_enabled ? MAX_REPACK_XIDS : 0"
not sure it is a real issue, but if EnableLogicalDecoding is called
somehow after allocating the array - it makes it possible to overrun
the array later by MAX_REPACK_XIDS.

------------------------------

src/backend/commands/cluster.c:3006

"apply_cxt = AllocSetContextCreate(TopTransactionContext,
                           "REPACK - apply",
                           ALLOCSET_DEFAULT_SIZES);"

Should we do it before the "MakeSingleTupleTableSlot" calls?
Because MakeSingleTupleTableSlot stored CurrentMemoryContext in tts_mcxt.

------------------------------

src/backend/commands/cluster.c:3187

if (natt_ext != 0)
    elog(WARNING, "have natt_ext %d, weird", natt_ext);

Should we make that ERROR?

------------------------------

src/backend/access/rmgrdesc/standbydesc.c:24

appendStringInfo(buf, "nextXid %u latestCompletedXid %u
oldestRunningXid %u oldestRunningXid %u",

"oldestRunningXidLogical" at the end?

------------------------------

src/backend/catalog/index.c:766,1464-1469

"bool      progress = (flags & INDEX_CREATE_REPORT_PROGRESS) != 0;"

AFAIU gin, hash and btree (at least) still just unconditionally write
PROGRESS_CREATEIDX_* progress.
------------------------------

src/backend/catalog/toasting.c:334

"INDEX_CREATE_IS_PRIMARY | INDEX_CREATE_REPORT_PROGRESS, 0,"

Should we add the "progress" flag too here and move it from make_new_heap?

-------------------------------

Also just, gently remind you about [1] and a simple way to avoid any
unnoticed MVCC-related issues with REPACK proposed here [2].

Best regards,
Mikhail.

[1]: https://www.postgresql.org/message-id/flat/5k2dfckyp6zv2fiovosvtbya5onvplgviz5n4kdamxupff4vi2%40yytzfnwr2ox7#c52bec0a074779921b14c1e46da9ed21
[2]: https://www.postgresql.org/message-id/CADzfLwUEH5+LjCN+6kRfSsXwuou8rKXyVV42Wi-O_TG0360Kug@mail.gmail.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