Re: Planning counters in pg_stat_statements (using pgss_store)

On Sun, Jan 5, 2020 at 7:02 PM legrand legrand
<[email protected]> wrote:
>
> Julien Rouhaud wrote
> > On Sun, Jan 5, 2020 at 4:11 PM legrand legrand
> > &lt;
>
> > legrand_legrand@
>
> > &gt; wrote:
> >>
> >> Hi Julien,
> >>
> >> I would like to create a link with
> >> https://www.postgresql.org/message-id/
>
> > [email protected]
>
> >>
> >> where we met an ASSET FAILURE because query text was not initialized ...
> >>
> >> The question raised is:
> >>
> >> - should query text be always provided
> >> or
> >> - if not how to deal that case (in pgss).
> >
> > I'd think that since the query text was until now always provided,
> > there's no reason why this patch should change that.  That being said,
> > there has been other concerns raised wrt. temporary tables in the IVM
> > patchset, so ISTM that there might be important architectural changes
> > upcoming, so having to deal with this case in pgss is not rushed
> > (especially since handling that in pgss would be trivial), and can
> > help to catch issue with the query text pasing.
>
> IVM revealed that ASSERT,
> but IVM works fine with pg_stat_statements.track_planning = off.

Yes, but on the other hand the current IVM patchset also adds the only
pg_plan_query call that don't provide a query text.  I didn't see any
other possibility, and if there are other cases they're unfortunately
not covered by the full regression tests.

> There may be others parts of postgresql that would have workede fine as
> well.
>
> This means 2 things:
> - there is a (litle) risk to meet other assert failures when using planning
> counters in pgss,
> - we have an easy workarround to fix it (disabling track_planning).
>
> But I would have prefered this new feature to work the same way with or
> without track_planning activated ;o(

Definitely, but fixing the issue in pgss (ignoring planner calls when
we don't have a query text) means that pgss won't give an exhaustive
view of activity anymore, so a fix in IVM would be a better solution.
Let's wait and see if Nagata-san and other people involved in that
have an opinion on it.