Re: Allow pg_read_all_stats to read pg_stat_progress_*

On Thu, Apr 16, 2020 at 7:05 AM Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
wrote:

> At Wed, 15 Apr 2020 15:58:05 +0500, "Andrey M. Borodin" <
> x4mmm(at)yandex-team(dot)ru> wrote in
> > > 15 апр. 2020 г., в 15:25, Magnus Hagander <magnus(at)hagander(dot)net>
> написал(а):
> > > I think that makes perfect sense. The documentation explicitly says
> "can read all pg_stat_* views", which is clearly wrong -- so either the
> code or the docs should be fixed, and it looks like it's the code that
> should be fixed to me.
> > Should it be bug or v14 feature?
> >
> > Also pgstatfuncs.c contains a lot more checks of
> has_privs_of_role(GetUserId(), beentry->st_userid).
> > Maybe grant them all?
> >
> > > As for the patch, one could argue that we should just store the
> resulting boolean instead of re-running the check (e.g. have a "bool
> has_stats_privilege" or such), but perhaps that's an unnecessary
> micro-optimization, like the attached.
> >
> > Looks good to me.
>
> pg_stat_get_activty checks (has_privs_of_role() ||
> is_member_of_role()) in-place for every entry. It's not necessary but
> I suppose that doing the same thing for pg_stat_progress_info might be
> better.
>

From a result perspective, it shouldn't make a difference though, should
it? It's a micro-optimization, but it might not have an actual performance
effect in reality as well, but the result should always be the same?

(FWIW, pg_stat_statements has a coding pattern similar to the one I
suggested in the patch)

>
> It's another issue, but pg_stat_get_backend_* functions don't consider
> pg_read_all_stats. I suppose that the functions should work under the
> same criteria to pg_stat views, and maybe explicitly documented?
>

That's a good question. They haven't been documented to do so, but it
certainly seems *weird* that the same information should be available
through a view like pg_stat_activity, but not through the functions.

I would guess this was simply forgotten in 25fff40798f -- I don't recall
any discussion about it. The commit message specifically says
pg_database_size() and pg_tablespace_size(), but mentions nothing about
pg_stat_*.

>
> If we do that, it may be better that we define "PGSTAT_VIEW_PRIV()" or
> something like and replace the all occurances of the idiomatic
> condition with it.
>

You mean something like the attached?

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>