Re: wake up logical workers after ALTER SUBSCRIPTION

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Cc: Melih Mutlu <m(dot)melihmutlu(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: wake up logical workers after ALTER SUBSCRIPTION
Date: 2023-01-05 06:04:37
Message-ID: CAA4eK1JFgvhxV448uNTkKpQpGe+X8WRWtyf45h4vASEpNz3Gkw@mail.gmail.com
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On Thu, Jan 5, 2023 at 10:16 AM Nathan Bossart <nathandbossart(at)gmail(dot)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.

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