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: 2023-01-05T06:04:37Z
Lists: pgsql-hackers 
On Thu, Jan 5, 2023 at 10:16 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Jan 04, 2023 at 08:12:37PM -0800, Nathan Bossart wrote:
> > On Thu, Jan 05, 2023 at 09:09:12AM +0530, Amit Kapila wrote:
> >> But there doesn't appear to be any guarantee that the result for
> >> AllTablesyncsReady() will change between the time it is invoked
> >> earlier in the function and at the place you have it in the patch.
> >> This is because the value of 'table_states_valid' may not have
> >> changed. So, how is this supposed to work?
> >
> > The call to CommandCounterIncrement() should set table_states_valid to
> > false if needed.
>
> In v12, I moved the restart for two_phase mode to the end of
> process_syncing_tables_for_apply() so that we don't need to rely on another
> iteration of the loop.
>

This should work but it is better to add a comment before calling
CommandCounterIncrement() to indicate that this is for making changes
to the relation state visible.

Thinking along similar lines, won't apply worker need to be notified
of SUBREL_STATE_SYNCWAIT state change by the tablesync worker?

-- 
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.