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From: Fujii Masao <masao.fujii@gmail.com>
Date: Tue, 7 Apr 2026 12:04:12 +0900
Message-ID: 
 <CAHGQGwFf+cpgw3T=NsGF8cxm4zx74AMCdajDda2Z7OXq9YM1mQ@mail.gmail.com>
Subject: Re: pgsql: Reduce log level of some logical decoding messages from
 LOG to D
To: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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 <https://www.postgresql.org/message-id/CAHGQGwFf%2Bcpgw3T%3DNsGF8cxm4zx74AMCdajDda2Z7OXq9YM1mQ%40mail.gmail.com>
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On Tue, Apr 7, 2026 at 1:16=E2=80=AFAM Robert Haas <robertmhaas@gmail.com> =
wrote:
> > But probably are you suggesting making this behavior the default? If ye=
s,
> > one straightforward approach to implement that would be to log these me=
ssages
> > at LOG when AmWalSenderProcess() or AmLogicalSlotSyncWorkerProcess() is=
 true,
> > and at DEBUG1 otherwise.
>
> Yeah.

OK, I've prepared a patch to implement this. Patch attached.
It introduces a LogicalDecodingLogLevel() macro to choose the log level
based on context, but the name may not be ideal, so suggestions are welcome=
.


> > The downside of this approach is that it becomes harder to suppress the=
se
> > messages for walsender or slotsync worker if some users want to do that=
.
> > For example, raising log_min_messages to FATAL or PANIC would suppress =
them,
> > but would also hide ERROR messages, which isn't desirable in production=
.
>
> I honestly don't know why anyone would want to do that. If these
> messages are showing up from background workers often enough to cause
> a problem, isn't something terribly wrong? It probably means your
> logical replication connections are constantly getting broken and
> having to be reestablished. The premise stated in the commit message
> is that these messages are simply too noisy, and that seems fair to
> me, because of the possibility of triggering them from SQL. But the
> idea that these aren't useful to a DBA when troubleshooting actual
> problems with logical replication seems quite incorrect to me.

Maybe. One such case is that, due to the issue discussed in [1], the slotsy=
nc
worker can generate those messages as frequently as every 200 ms. But once
that is fixed, it emits them only once per sync cycle, with intervals rangi=
ng
from MIN_SLOTSYNC_WORKER_NAPTIME_MS (200 ms) to
MAX_SLOTSYNC_WORKER_NAPTIME_MS (30 s), which might not generate
excessive log volume. At that point, it might be OK if messages from
background activity are not easily suppressible.

Regards,

[1] https://postgr.es/m/CAHGQGwF6zG9Z8ws1yb3hY1VqV-WT7hR0qyXCn2HdbjvZQKufDw=
@mail.gmail.com

--=20
Fujii Masao

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