Horton

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

shveta malik <shveta.malik@gmail.com>

View thread
From: shveta malik <shveta.malik@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2025-06-23T10:02:42Z
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.

On Mon, Jun 23, 2025 at 1:41 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> Given the discussion so far, it seems we might want to have a
> safeguard to prevent the effective_wal_level from being dropped to
> 'replica' if the last logical slot is accidentally dropped.

Yes, needed for cases where standby or cascaded standbys have
requirements of logical decoding.

> Another
> idea we can consider is that we automatically increase
> effective_wal_level to 'logical' upon the logical slot creation but
> don't automatically decrease it when dropping the last slot. To
> decrease the effective_wal_level to 'replica', users would need to do
> that explicitly for example using a SQL function,
> pg_disable_logical_decoding().

Okay. Seems a good solution so far.

> We might want to have a GUC parameter
> for users to turn on/off this automatic behavior.
>

Yes. Agreed.

thanks
Shveta