Date: Sun, 18 Oct 2020 00:01:42 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Julien Rouhaud <rjuju123@gmail.com>, Bruce Momjian <bruce@momjian.us>,
	Robert Haas <robertmhaas@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	torikoshia <torikoshia@oss.nttdata.com>,
	Atsushi Torikoshi <atorik@gmail.com>,
	Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>,
	Evgeny Efimkin <efimkin@yandex-team.ru>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Feature improvement: can we add queryId for
 pg_catalog.pg_stat_activity view?
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On 2020-Oct-17, Tom Lane wrote:

> Fair point, but if we allow several different values to be set in
> different sessions, what ends up happening in pg_stat_statements?
> 
> On the other hand, maybe that's just a matter for documentation.
> "If the 'same' query is processed with two different queryID settings,
> that will generally result in two separate table entries, because
> the same ID hash is unlikely to be produced in both cases".

Wait ... what?  I've been thinking that this GUC is just to enable or
disable the computation of query ID, not to change the algorithm to do
so.  Do we really need to allow different algorithms in different
sessions?