Re: compute_query_id and pg_stat_statements

At Thu, 13 May 2021 10:02:45 +0800, Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote in
> On Thu, May 13, 2021 at 10:51:52AM +0900, Kyotaro Horiguchi wrote:
> > At Thu, 13 May 2021 09:59:43 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> > > How about adding a GUC_INTERNAL "current_query_provider" or such?
> >
> > On the second thought, I wonder why we don't just call JumbleQuery in
> > pgss_post_parse_analyze when compute_query_id is "off".
>
> Because not generating a query_id for a custom query_id implementation is a
> valid use case for queries that are known to lead to huge pg_stat_statements
> overhead, as I mentioned in [1]. For the record I implemented that in
> pg_queryid (optionally don't generate query_id for queries referencing a temp
> relation) yesterday evening as a POC for that approach.

Yes, I know. So I said that "if not yet called". I believe any "real"
alternative query-id provider is supposed to be hooked "before"
pg_stat_statements. (It is a kind of magic to control the order of
plugins, though..) When the alternative provider generated a query_id
(that is, it has set jstate), pg_stat_statment doesn't call the
in-core JumbleQuery and uses the givin query_id.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center