Re: System username in pg_stat_activity

Hi,

On 2024-02-16 20:57:59 +0100, Magnus Hagander wrote:
> On Fri, Feb 16, 2024 at 8:41 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2024-01-10 12:46:34 +0100, Magnus Hagander wrote:
> > > The attached patch adds a column "authuser" to pg_stat_activity which
> > > contains the username of the externally authenticated user, being the
> > > same value as the SYSTEM_USER keyword returns in a backend.
> >
> > I continue to think that it's a bad idea to make pg_stat_activity ever wider
> > with columns that do not actually describe properties that change across the
> > course of a session. Yes, there's the argument that that ship has sailed, but
> > I don't think that's a good reason to continue ever further down that road.
> >
> > It's not just a usability issue, it also makes it more expensive to query
> > pg_stat_activity. This is of course more pronounced with textual columns than
> > with integer ones.
>
> That's a fair point, but I do think that has in most ways already sailed, yes.
>
> I mean, we could split it into more than one view. But adding a new
> view for every new thing we want to show is also not very good from
> either a usability or performance perspective. So where would we put
> it?

I think we should group new properties that don't change over the course of a
session ([1]) in a new view (e.g. pg_stat_session). I don't think we need one
view per property, but I do think it makes sense to split information that
changes very frequently (like most pg_stat_activity contents) from information
that doesn't (like auth_method, auth_identity).

Greetings,

Andres Freund

[1]

Additionally I think something like pg_stat_session could also contain
per-session cumulative counters like the session's contribution to
pg_stat_database.{idle_in_transaction_time,active_time}