Horton

Re: POC: enable logical decoding when wal_level = 'replica' without a server restart

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: shveta malik <shveta.malik@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Shlok Kyal <shlok.kyal.oss@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2025-09-25T19:15:27Z
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. Fix regression test failure when wal_level is set to minimal.

  2. Toggle logical decoding dynamically based on logical slot presence.

  3. Disallow server start with sync_replication_slots = on and wal_level < logical.

Attachments

On Thu, Sep 25, 2025 at 4:57 AM shveta malik <shveta.malik@gmail.com> wrote:
>
> On Tue, Sep 23, 2025 at 3:28 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> >
> > I've attached the updated patch. It incorporates all comments I got so
> > far and implements to lazily disable logical decoding. It's used only
> > when the process tries to disable logical decoding during process
> > exit.
> >
>
> I am resuming the review now. I agree with the discussion of lazily
> disabling logical decoding on ERROR or process-exit for temp-slot.
>
> Few  initial comments:

Thank you for the comments!

>
> 1)
> I see that on standby too, during proc-exit, we set 'pending_disable'.
> But it never resets it, as DisableLogicalDecodingIfNecessary is no-op
> on standby. And thus the checkpoint keeps on attempting to reset it
> everytime. Do we even need to set it on standby?
>
> Logfile has repeated: 'start completing pending logical decoding
> disable request'

Ugh, I missed that part. I think that standbys should not delegate the
deactivation to the checkpointer uless the deactivation is actually
required.

> 2)
> + ereport(LOG,
> + (errmsg("skip disabling logical decoding as during process exit")));
>
> 'as' not needed.

I've fixed the above two points and attached the new version patch.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com