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From: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Date: Sat, 21 Mar 2026 01:15:54 -0700
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 <CAHg+QDfLh-yb+OacN6qPYF6H3SPDmVJUiors7vkSMq4yxfhNrA@mail.gmail.com>
Subject: Re: log XLogPrefetch stats at end of recovery
To: Lakshmi N <lakshmin.jhs@gmail.com>
Cc: pgsql-hackers@postgresql.org
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Hi,

On Wed, Mar 18, 2026 at 12:18=E2=80=AFAM Lakshmi N <lakshmin.jhs@gmail.com>=
 wrote:

> Hi,
>
> While investigating a long recovery, I noticed that XLogPrefetch stats
> were not logged at the end of recovery. This log message will be useful t=
o
> understand how effective XLogPrefetch was during recovery. Adding a patch
> to address this.
>

Applied this patch and validated the log message. This log message appears
to be useful to me, particularly while doing fleet wide analysis. I am
wondering if we can periodically log this in standby mode as well, not just
before promoting?

2026-03-20 23:33:13.756 PDT [2265441] LOG:  XLogPrefetcher stats:
prefetch=3D14, hit=3D6, skip_init=3D5, skip_new=3D28, skip_fpw=3D18, skip_r=
ep=3D996

Thanks,
Satya

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<div><div dir=3D"ltr"><div dir=3D"ltr"><div>Hi,</div></div></div></div><div=
><div><br></div><div>On Wed, Mar 18, 2026 at 12:18=E2=80=AFAM Lakshmi N &lt=
;<a href=3D"mailto:lakshmin.jhs@gmail.com" target=3D"_blank">lakshmin.jhs@g=
mail.com</a>&gt; wrote:</div></div><div><div class=3D"gmail_quote"></div></=
div><div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8e=
x;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-lef=
t-color:rgb(204,204,204)"><div dir=3D"ltr">Hi,<div><br></div><div>While inv=
estigating a long recovery, I noticed that XLogPrefetch stats were not logg=
ed at the end of recovery. This log message will be useful to understand ho=
w effective XLogPrefetch was during recovery. Adding a patch to address thi=
s.</div></div></blockquote><div><br></div></div><div><div>Applied this patc=
h and validated the log message. This log message appears to be useful to m=
e,=C2=A0particularly while doing fleet wide analysis. I am wondering if we =
can periodically log this in standby mode as well,=C2=A0not=C2=A0just befor=
e promoting?</div><div><br></div><div>2026-03-20 23:33:13.756 PDT [2265441]=
 LOG: =C2=A0XLogPrefetcher stats: prefetch=3D14, hit=3D6, skip_init=3D5, sk=
ip_new=3D28, skip_fpw=3D18, skip_rep=3D996=C2=A0</div><div><br></div><div>T=
hanks,</div><div>Satya</div>
</div>

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