Re: Add callback in pgstats for backend initialization

Hi,

On Tue, Sep 03, 2024 at 10:52:20AM +0900, Michael Paquier wrote:
> Hi all,
>
> Currently, the backend-level initialization of pgstats happens in
> pgstat_initialize(), where we are using a shortcut for the WAL stats,
> with pgstat_init_wal().
>
> I'd like to propose to add a callback for that, so as in-core or
> custom pgstats kinds can assign custom actions when initializing a
> backend. The use-case I had for this one are pretty close to what we
> do for WAL, where we would rely on a difference of state depending on
> what may have existed before reaching the initialization path. So
> this can offer more precision. Another case, perhaps less
> interesting, is to be able to initialize some static backend state.

I think the proposal makes sense and I can see the use cases too, so +1.

> This gives the simple patch
> attached.

Should we add a few words about this new callback (and the others in
PgStat_KindInfo while at it) in the "Custom Cumulative Statistics" section of
xfunc.sgml?

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com