Horton

Re: wake up logical workers after ALTER SUBSCRIPTION

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Melih Mutlu <m.melihmutlu@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2023-01-03T06:13:59Z
Lists: pgsql-hackers 
On Wed, Dec 7, 2022 at 11:42 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Dec 07, 2022 at 02:07:11PM +0300, Melih Mutlu wrote:
> > Do we also need to wake up all sync workers too? Even if not, I'm not
> > actually sure whether doing that would harm anything though.
> > Just asking since currently the patch wakes up all workers including sync
> > workers if any still exists.
>
> After sleeping on this, I think we can do better.  IIUC we can simply check
> for AllTablesyncsReady() at the end of process_syncing_tables_for_apply()
> and wake up the logical replication workers (which should just consiѕt of
> setting the current process's latch) if we are ready for two_phase mode.
>

How just waking up will help with two_phase mode? For that, we need to
restart the apply worker as we are doing at the beginning of
process_syncing_tables_for_apply().

-- 
With Regards,
Amit Kapila.

Commits

  1. Avoid type cheats for invalid dsa_handles and dshash_table_handles.

  2. Track logrep apply workers' last start times to avoid useless waits.

  3. Check for two_phase change at end of process_syncing_tables_for_apply.

  4. Wake up a subscription's replication worker processes after DDL.