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From: Fujii Masao <masao.fujii@gmail.com>
Date: Tue, 17 Mar 2026 11:00:38 +0900
Message-ID: 
 <CAHGQGwFzg9J_z71kwnjXOxaoO3upMW8RdT4ieE8MBLq6h-ojZg@mail.gmail.com>
Subject: Re: pg_stat_replication.*_lag sometimes shows NULL during active
 replication
To: Shinya Kato <shinya11.kato@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Mon, Mar 16, 2026 at 9:26=E2=80=AFAM Shinya Kato <shinya11.kato@gmail.co=
m> wrote:
> Thank you for the v4 patch. I think this approach is better than mine.
> I tested the patch and confirmed that the issue no longer reproduces
> with physical replication. However, with logical replication, the lag
> columns in pg_stat_replication still show NULL periodically at
> wal_receiver_status_interval, since send_feedback() in worker.c can
> still send duplicate positions.

I was thinking that if a feedback message triggered by
wal_receiver_status_interval has the same LSNs as the previous message,
it's expected for the lag columns to become NULL. But you see it differentl=
y,
don't you? Sorry, I failed to understand your point...

Regards,

--=20
Fujii Masao