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From: Lukas Fittl <lukas@fittl.com>
Date: Tue, 24 Mar 2026 23:54:18 -0700
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 <CAP53PkwgM5P2e-LN2BdOK3NCWhbK-u5H01qNYN9nuStLH0m6ew@mail.gmail.com>
Subject: Re: pg_buffercache: Add per-relation summary stats
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Hi Bertrand,

Thanks for your review, and sorry it took me a while to get to it -
other patches took more of my attention unexpectedly.

On Mon, Mar 9, 2026 at 2:15=E2=80=AFAM Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:
> =3D=3D=3D 1
>
> +typedef struct
> +{
> +   RelFileNumber relfilenumber;
> +   Oid         reltablespace;
> +   Oid         reldatabase;
> +   ForkNumber  forknum;
> +} BufferRelStatsKey;
>
> What about making use of RelFileLocator (instead of 3 members relfilenumb=
er,
> reltablespace and reldatabase)?

Agreed, and noted by others later too - will adjust.

> +  <para>
> +   The <function>pg_buffercache_relation_stats()</function> function ret=
urns a
> +   set of rows summarizing the state of all shared buffers, aggregated b=
y
> +   relation and fork number.  Similar and more detailed information is
> +   provided by the <structname>pg_buffercache</structname> view, but
> +   <function>pg_buffercache_relation_stats()</function> is significantly
> +   cheaper.
> +  </para>
>
> I'm not 100% sure about the name of the function since the stats are "res=
et"
> after a rewrite. What about pg_buffercache_relfilenode or
> pg_buffercache_aggregated?

I'll gone with "pg_buffercache_relations" for now in v2, but I could
also see "pg_buffercache_relfilenodes" making sense, if we wanted to
be more clear about the fact that these are physical relation files,
not logical relations.

Thanks,
Lukas

--=20
Lukas Fittl