Date: Mon, 12 Oct 2020 16:53:40 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
	Julien Rouhaud <rjuju123@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	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 Mon, Oct 12, 2020 at 04:07:30PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > On Mon, Oct 12, 2020 at 02:26:15PM -0400, Tom Lane wrote:
> >> Yeah, I agree --- a version number is the wrong way to think about this.
> 
> > The version number was to invalidate _all_ query hashes if the
> > algorithm is slightly modified, rather than invalidating just some of
> > them, which could lead to confusion.
> 
> Color me skeptical as to the use-case for that.  From users' standpoints,
> the hash is mainly going to change when we change the set of parse node
> fields that get hashed.  Which is going to happen at every major release
> and no (or at least epsilon) minor releases.  So I do not see a point in
> tracking an algorithm version number as such.  Seems like make-work.

OK, I came up with the hash idea only to address one of your concerns
about mismatched hashes for algorithm improvements/changes.  Seems we
might as well just document that cross-version hashes are different.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee