From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, 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>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, 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: | 2020-10-06 02:18:19 |
Message-ID: | 20201006021819.GA10975@momjian.us |
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Lists: | pgsql-hackers |
On Mon, Oct 5, 2020 at 07:58:42PM -0300, Álvaro Herrera wrote:
> On 2020-Oct-05, Tom Lane wrote:
>
> > FWIW, I think this proposal is a mess. I was willing to hold my nose
> > and have a queryId field in the internal Query struct without any solid
> > consensus about what its semantics are and which extensions get to use it.
> > Exposing it to end users seems like a bridge too far, though. In
> > particular, I'm afraid that that will cause people to expect it to have
> > consistent values across PG versions, or even just across architectures
> > within one version.
>
> I wonder if it would help to purposefully change the computation so that
> it is not -- for instance, hash the system_identifier as initial value.
> Then users would be forced to accept that it'll change as soon as it
> migrates to another server or is upgraded to a new major version.
That seems like a good idea, but it would prevent cross-cluster
same-major-version comparisons, which seems like a negative. Perhaps we
should add the major version into the hash to handle this. Ideally,
let's just put a queryid-hash-version into to the hash, so if we change
the computation, we just update the hash version and nothing matches
anymore.
I do think the queryid has to display independent of pg_stat_statements,
because I can see people using queryid for log file and pg_stat_activity
comparisons. I also think the ability to have queryid accessible is an
important feature outside of pg_stat_statements, so I do think we need a
way to move this idea forward.
--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EnterpriseDB https://enterprisedb.com
The usefulness of a cup is in its emptiness, Bruce Lee
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