Horton

Re: Adding REPACK [concurrently]

Antonin Houska <ah@cybertec.at>

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From: Antonin Houska <ah@cybertec.at>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>, Fujii Masao <masao.fujii@gmail.com>
Date: 2025-09-01T15:30:18Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Improve REPACK (CONCURRENTLY) error messages some more

  2. Add CONCURRENTLY option to REPACK

  3. Make index_concurrently_create_copy more general

  4. Document the 'command' column of pg_stat_progress_repack

  5. Introduce the REPACK command

  6. Split vacuumdb to create vacuuming.c/h

  7. Revert changes to CONCURRENTLY that "sped up" Xmin advance

Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> Antonin Houska <ah@cybertec.at>:
> > Are you sure the test is complete? I see no occurrence of the REPACK command
> > in it.
> Oops, send invalid file. The correct one in attachment.

Thanks!

The problem was that when removing the original "preserve visibility patch"
v12-0005 [1] from the series, I forgot to change the value of
'need_full_snapshot' argument of CreateInitDecodingContext().

v12 and earlier treated the repacked table like system catalog, so it was
o.k. to pass need_full_snapshot=false. However, it must be true now, otherwise
the snapshot created for the initial copy does not see commits of transactions
that do not change regular catalogs.

The fix is as simple as

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index f481a3cec6d..7866ac01278 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -502,6 +502,7 @@ SnapBuildInitialSnapshotForRepack(SnapBuild *builder)
        StringInfo      buf = makeStringInfo();
 
        Assert(builder->state == SNAPBUILD_CONSISTENT);
+       Assert(builder->building_full_snapshot);
 
        snap = SnapBuildBuildSnapshot(builder);
 

I'll apply it to the next version of the "Add CONCURRENTLY option to REPACK
command" patch.


[1] https://www.postgresql.org/message-id/flat/CAFj8pRDK89FtY_yyGw7-MW-zTaHOCY4m6qfLRittdoPocz+dMQ@mail.gmail.com

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com