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

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Julien Rouhaud <julien(dot)rouhaud(at)free(dot)fr>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Bruce Momjian <bruce(at)momjian(dot)us>, 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: 2020-02-01 11:30:45
Message-ID: 20200201113045.x4qj36uvt34ymwiy@development
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On Fri, Nov 29, 2019 at 09:39:09AM +0100, Julien Rouhaud wrote:
>On Fri, Nov 29, 2019 at 7:21 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>> On Fri, Nov 29, 2019 at 03:19:49PM +0900, Michael Paquier wrote:
>> > On Wed, Nov 13, 2019 at 12:53:09PM +0100, Julien Rouhaud wrote:
>> >> I'd really like to have the queryid function available through SQL,
>> >> but I think that this specific case wouldn't work very well for
>> >> pg_stat_statements' approach as it's working with oid. The query
>> >> string in pg_stat_activity is the user provided one rather than a
>> >> fully-qualified version, so in order to get that query's queryid, you
>> >> need to know the exact search_path in use in that backend, and that's
>> >> not something available.
>> >
>> > Yeah.. So, we have a patch marked as ready for committer here, and it
>> > seems to me that we have a couple of issues to discuss more about
>> > first particularly this query ID of 0. Again, do others have more
>> > any input to offer?
>I just realized that with current infrastructure it's not possible to
>display a utility queryid. We need to recognize utility to not
>process the counters twice (once in processUtility, once in the
>underlying executor), so we don't provide a queryid for utility
>statements in parse analysis. Current magic value 0 has the side
>effect of showing an invalid queryid for all utilty statements, and
>using a magic value different from 0 will just always display that
>magic value. We could instead add another field in the Query and
>PlannedStmt structs, say "int queryid_flags", that extensions could
>use for their needs?
>> And while on it, the latest patch does not apply, so a rebase is
>> needed here.
>Yep, I noticed that this morning. I already rebased the patch
>locally, I'll send a new version with new modifications when we reach
>an agreement on the utility issue.

Well, this patch was in WoA since November, but now that I look at it
that might have been wrong - we're clearly waiting for agreement on how
to handle queryid for utility commands. I suspect the WoA status might
have been driving people away from this thread :-(

I've switched the patch to "needs review" and moved it to the next CF.
What I think needs to happen is we get a patch implementing one of the
proposed solutions, and discuss that.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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