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From: Shinya Kato <shinya11.kato@gmail.com>
Date: Thu, 26 Mar 2026 14:40:37 +0900
Message-ID: 
 <CAOzEurT7E4fX5jrHza4+BZt5krEc-0b0vXdHRNCjwNnrDy8g_Q@mail.gmail.com>
Subject: Re: pg_stat_replication.*_lag sometimes shows NULL during active
 replication
To: Fujii Masao <masao.fujii@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Thu, Mar 26, 2026, 00:30 Fujii Masao <masao.fujii@gmail.com> wrote:

> On Wed, Mar 25, 2026 at 4:03=E2=80=AFPM Shinya Kato <shinya11.kato@gmail.=
com>
> wrote:
> > Thanks for the updated patch. LGTM.
> >
> > Regarding the backpatch, I'd personally appreciate it if the walsender.=
c
> changes were backpatched to stable branches. As you noted, it don't fully
> solve the reported issue, but they do help reduce the cases where lag
> columns in pg_stat_replication unexpectedly become NULL.
> >
> > Even a partial mitigation in the back branches would be valuable for
> users running stable releases.
>
> +1
>
> I've split the changes into two patches.
>
> Patch 0001 fixes premature NULL lag reporting in walsender. I will commit
> it
> and backpatch it to all supported branches.
>
> Patch 0002 avoids sending duplicate WAL locations in standby status
> replies.
> I will commit this to master only.
>

Thanks, LGTM.

Best regards,
Shinya Kato

>

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<div dir=3D"auto"><div><br><br><div class=3D"gmail_quote gmail_quote_contai=
ner"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, Mar 26, 2026, 00:30 Fuji=
i Masao &lt;<a href=3D"mailto:masao.fujii@gmail.com">masao.fujii@gmail.com<=
/a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0=
 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Wed, Mar 25, 2026=
 at 4:03=E2=80=AFPM Shinya Kato &lt;<a href=3D"mailto:shinya11.kato@gmail.c=
om" target=3D"_blank" rel=3D"noreferrer">shinya11.kato@gmail.com</a>&gt; wr=
ote:<br>
&gt; Thanks for the updated patch. LGTM.<br>
&gt;<br>
&gt; Regarding the backpatch, I&#39;d personally appreciate it if the walse=
nder.c changes were backpatched to stable branches. As you noted, it don=
9;t fully solve the reported issue, but they do help reduce the cases where=
 lag columns in pg_stat_replication unexpectedly become NULL.<br>
&gt;<br>
&gt; Even a partial mitigation in the back branches would be valuable for u=
sers running stable releases.<br>
<br>
+1<br>
<br>
I&#39;ve split the changes into two patches.<br>
<br>
Patch 0001 fixes premature NULL lag reporting in walsender. I will commit i=
t<br>
and backpatch it to all supported branches.<br>
<br>
Patch 0002 avoids sending duplicate WAL locations in standby status replies=
.<br>
I will commit this to master only.<br></blockquote></div></div><div dir=3D"=
auto"><br></div><div dir=3D"auto">Thanks, LGTM.</div><div dir=3D"auto"><br>=
</div><div dir=3D"auto">Best regards,</div><div dir=3D"auto">Shinya Kato</d=
iv><div dir=3D"auto"><div class=3D"gmail_quote gmail_quote_container"><bloc=
kquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #cc=
c solid;padding-left:1ex">
</blockquote></div></div></div>

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