Re: compute_query_id and pg_stat_statements

On Wed, May 12, 2021 at 11:42:12AM +0200, Pavel Stehule wrote:
> st 12. 5. 2021 v 11:39 odesílatel Kyotaro Horiguchi <horikyota.ntt@gmail.com>
> napsal:
> 
> > At Wed, 12 May 2021 17:30:26 +0800, Julien Rouhaud <rjuju123@gmail.com>
> > wrote in
> > > On Wed, May 12, 2021 at 10:57:25AM +0200, Pavel Stehule wrote:
> > > >
> > > > My second proposal can work for your example too. pg_stat_statements
> > have
> > > > to require any active queryid computing. And when it is not available,
> > then
> > > > the exception should be raised.
> > > >
> > > > The custom queryid can return null, and still the queryid will be
> > computed.
> > > > Maybe the warning can be enough. Just, if somebody use
> > pg_stat_statements
> > > > function, then enforce the check if queryid is computed
> > (compute_query_id
> > > > is true || some hook is not null), and if not then raise a warning.
> > >
> > > Ah I'm sorry I misunderstood your proposal.  Yes, definitely adding a
> > warning
> > > or an error when executing pg_stat_statements() SRF would help, that's a
> > great
> > > idea!
> > >
> > > I'll wait a bit in case someone has any objection, and if not send an
> > updated
> > > patch!
> >
> > Isn't there a case where pg_stat_statements uses an alternative
> > query-id provider?
> >
> 
> this check just can check if there is "any" query-id provider. In this
> context is not important if it is buildin or external

Yes, the idea is that if you execute "SELECT * FROM pg_stat_statements" or
similar, then if the executing query itself doesn't have a queryid then
it's very likely that you didn't configure compute_query_id or an alternative
query_id implementation properly.  And loudly complaining seems like the right
thing to do.