Re: compute_query_id and pg_stat_statements

Julien Rouhaud <rjuju123(at)gmail(dot)com> writes:
> On Sat, Apr 24, 2021 at 01:43:51PM -0400, Tom Lane wrote:
>> I haven't looked, but did we put anything into pg_stat_statements
>> to make it easy to tell if you've messed up this setting?

> You mean apart from from having pg_stat_statements' view/SRFs returning
> nothing?

> I think it's a reasonable use case to sometime disable query_id calculation,
> eg. if you know that it will only lead to useless bloat in the entry and that
> you won't need the info, so spamming warnings if there are no queryid could
> cause some pain.

I agree repeated warnings would be bad news. I was wondering if we could
arrange a single warning at the time pg_stat_statements is preloaded into
the postmaster. In this way, if you tried to use a configuration file
that used to work, you'd hopefully get some notice about why it no longer
does what you want. Also, if you are preloading pg_stat_statements, it
seems reasonable to assume that you'd like the global value of the flag
to be "on", even if there are use-cases for transiently disabling it.

I think the way to detect "being loaded into the postmaster" is
if (IsPostmasterEnvironment && !IsUnderPostmaster)

regards, tom lane