Re: compute_query_id and pg_stat_statements

Le jeu. 13 mai 2021 à 12:26, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> a
écrit :

> At Thu, 13 May 2021 12:11:12 +0900 (JST), Kyotaro Horiguchi <
> horikyota(dot)ntt(at)gmail(dot)com> wrote in
> > As the result, even if we take the DLL approach, still not need to
> > split out the query-id provider part. By the following config:
> >
> > > query_id_provider = 'pg_stat_statements'
> >
> > the core can obtain the entrypoint of, say, "_PG_calculate_query_id"
> > to call it. And it can be of another module.
> >
> > It seems like the only problem doing that is we don't have a means to
> > call per-process intializer for a preload libralies.
>
> So this is a crude PoC of that.
>
> pg_stat_statemnts defines its own query-id provider function in
> pg_stat_statements which calls in-core DefaultJumbeQuery (end emits a
> log line).
>
> If server started with query_id_provider='auto' and pg_stat_statements
> is not loaded, pg_stat_activity.query_id is null.
>
> If query_id_provider='auto' and pg_stat_statements is loaded,
> pg_stat_activity.query_id is filled in with a query id.
>
> If query_id_provider='default' or 'pg_stat_statements' and
> pg_stat_statements is not loaded, pg_stat_activity.query_id is filled
> in with a query id.
>
> If query_id_provider='none' and pg_stat_statements is loaded, it
> complains as "query id provider is not available" and refuss to start.
>
> If showing the variable, it shows the real provider name instead of
> the setting in postgresql.conf.
>

what if you want to have some other extensions like pg_stat_kcache or
pg_store_plans that need a query_id but don't really care if
pg_stat_statements is enabled or not? should they all declare their own
wrapper too? should the system complain or silently ignore when they all
try to install their provider function?

>