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From: Sami Imseih <samimseih@gmail.com>
Date: Thu, 23 Oct 2025 19:57:38 -0500
Message-ID: 
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Subject: Re: [Proposal] Adding callback support for custom statistics kinds
To: Michael Paquier <michael@paquier.xyz>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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> On Thu, Oct 23, 2025 at 04:35:58PM -0500, Sami Imseih wrote:
> > Perhaps if someone wants to have separate files for each different
> > types of data,
> > we should be able to support multiple files. I think we can add an
> > option for the
> > number of files and they can then be named "pgstat.<kind>.1.stat",
> > pgstat.<kind>.2.stat",
> > etc. I rather avoid having the extension provide a set of files names.
> > So as arguments to the callback, besides the main file pointer ( as
> > you mention below),
> > we also provide the list of custom file pointers.
> >
> > what do you think?
>
> My worry here is the lack of flexibility regarding stats that could be
> split depending on the objects whose data needs to be flushed.  For
> example, stats split across multiple databases (like our good-old
> pre-v14 pgstats, but on a per-kind basis).  So I don't think that we
> can really assume that the list of file names should be fixed when we
> begin the read/write process of the main pgstats file.

I was trying to avoid an extra field in PgStat_KindInfo if possible, but
it's worthwhile to provide more flexibility to an extension. I will go
with this.

--
Sami Imseih
Amazon Web Services (AWS)