Re: Feature improvement: can we add queryId for pg_catalog.pg_stat_activity view?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, torikoshia <torikoshia(at)oss(dot)nttdata(dot)com>, Atsushi Torikoshi <atorik(at)gmail(dot)com>, Tatsuro Yamada <tatsuro(dot)yamada(dot)tf(at)nttcom(dot)co(dot)jp>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Evgeny Efimkin <efimkin(at)yandex-team(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Feature improvement: can we add queryId for pg_catalog.pg_stat_activity view?
Date: 2020-10-12 18:26:15
Message-ID: 3199563.1602527175@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> I don't really understand how a version number helps. It's not like
> there is going to be a v2 that is in all ways better than v1. If there
> are different algorithms here, they are going to be customized for
> different needs.

Yeah, I agree --- a version number is the wrong way to think about this.
It's gonna be more like algorithm foo versus algorithm bar versus
algorithm baz, where each one is better for a specific set of use-cases.
Julien already noted the point about hashing object OIDs versus object
names; one can easily imagine disagreeing with pg_stat_statement's
choices about ignoring values of constants; other properties of statements
might be irrelevant for some use-cases; and so on.

I'm okay with moving pg_stat_statement's existing algorithm into core as
long as there's a way for extensions to override it. With proper design,
that would allow extensions that do override it to coexist with
pg_stat_statements (thereby redefining the latter's idea of which
statements are "the same"), which is something that doesn't really work
nicely today.

regards, tom lane

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