Re: compute_query_id and pg_stat_statements

On Thu, May 13, 2021 at 8:38 AM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
>
> On Thu, May 13, 2021 at 08:32:50AM -0700, Maciek Sakrejda wrote:
> >
> > The warning makes it clear that there's something wrong, but not how
> > to fix it
>
> I'm confused, are we talking about the new warning in v2 as suggested by Pavel?
> As it should make things quite clear:
>
> +SELECT count(*) FROM pg_stat_statements;
> +WARNING: Query identifier calculation seems to be disabled
> +HINT: If you don't want to use a third-party module to compute query identifiers, you may want to enable compute_query_id
>
> The wording can of course be improved.

I meant that no warning can be as clear as things just working, but I
do have feedback on the specific message here:

* "seems to" be disabled? Is it? Any reason not to be more definitive here?
* On reading the beginning of the hint, I can see users asking
themselves, "Do I want to use a third-party module to compute query
identifiers?"
* "may want to enable"? Are there any situations where I don't want
to use a third-party module *and* I don't want to enable
compute_query_id?

So maybe something like

> +SELECT count(*) FROM pg_stat_statements;
> +WARNING: Query identifier calculation is disabled
> +HINT: You must enable compute_query_id or configure a third-party module to compute query identifiers in order to use pg_stat_statements.

(I admit "configure a third-party module" is pretty vague, but I think
that suggests it's only an option to consider if you know what you're
doing.)

Also, if you're configuring this for usage with a tool like pganalyze,
and neglect to run a manual query (we guide users to do that, but they
may skip that step), the warnings may not even be visible (the Go
driver we are using does not surface client warnings). Should this be
an error instead of a warning? Is it ever useful to get an empty
result set from querying pg_stat_statements? Using an error here would
parallel the behavior of shared_preload_libraries not including
pg_stat_statements.