Horton

Re: Adding REPACK [concurrently]

Mikhail Nikalayeu <mihailnikalayeu@gmail.com>

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From: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
To: Antonin Houska <ah@cybertec.at>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2025-12-18T02:05:00Z
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

Hello, Antonin!

On Sat, Dec 13, 2025 at 8:39 PM Antonin Houska <ah@cybertec.at> wrote:
> > ---
> > > SpinLockAcquire(&shared->mutex);
> > > valid = shared->sfs_valid;
> > > SpinLockRelease(&shared->mutex);
> >
> > Better to remember last_exported here to avoid any races/misses.
>
> What races/misses exactly?

Just as some way to reduce a number of potential scenarios/states
between parallel actors.

> > ---
> > > bool       done;
> >
> > bool exit_after_lsn_upto?
>
> Not sure.

I think it should be named in some way to signal it is a request, not a report.

> > Also, should we add some kind of back pressure between building
> > indexes/new heap and num of WAL we have?
> > But probably it is out of scope of the patch.
>
> Do you mean that the decoding worker should be less active if the amount of
> WAL doesn't grow too fast?

In the previous version (without background) we have some kind of
back-pressure during the scan part (if we have too muchWAL delayed
because of us - we process it).
But it is not more true with a background worker. At the same time -
it never was during the index building phase...

Best regards,
Mikhail.