Re: Warning about using pg_stat_reset() and pg_stat_reset_shared()

On Wed, Oct 5, 2022 at 11:07:49AM +1300, David Rowley wrote:
> On Thu, 29 Sept 2022 at 04:45, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >
> > We have discussed the problems caused by the use of pg_stat_reset() and
> > pg_stat_reset_shared(), specifically the removal of information needed
> > by autovacuum. I don't see these risks documented anywhere. Should we
> > do that? Are there other risks?
>
> There was some discussion in [1] a few years back. A few people were
> for the warning. Nobody seemed to object to it. There's a patch in
> [2].
>
> David
>
> [1] https://www.postgresql.org/message-id/flat/CAKJS1f8DTbCHf9gedU0He6ARsd58E6qOhEHM1caomqj_r9MOiQ%40mail.gmail.com
> [2] https://www.postgresql.org/message-id/CAKJS1f80o98hcfSk8j%3DfdN09S7Sjz%2BvuzhEwbyQqvHJb_sZw0g%40mail.gmail.com

Ah, good point. I have slightly reworded the doc patch, attached.
However, the last line has me confused:

A database-wide <command>ANALYZE</command> is recommended after
the statistics have been reset.

As far as I can tell, analyze updates pg_statistics values, but not
pg_stat_all_tables.n_dead_tup and n_live_tup, which are used by
autovacuum to trigger vacuum operations. I am afraid we have to
recommand VACUUM ANALYZE after pg_stat_reset(), no?

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

Indecision is a decision. Inaction is an action. Mark Batterson