Horton

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

Julien Rouhaud <rjuju123@gmail.com>

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From: Julien Rouhaud <rjuju123@gmail.com>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>, Bruce Momjian <bruce@momjian.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Tom Lane <tgl@sss.pgh.pa.us>, Nitin Jadhav <nitinjadhavpostgres@gmail.com>, Hannu Krosing <hannuk@google.com>, Robert Haas <robertmhaas@gmail.com>, Pavel Stehule <pavel.stehule@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>, Magnus Hagander <magnus@hagander.net>
Date: 2021-07-13T06:10:23Z
Lists: pgsql-hackers 
On Mon, Jul 12, 2021 at 10:02:59PM +0200, Peter Eisentraut wrote:
> On 22.04.21 11:23, Julien Rouhaud wrote:
> >      The statistics gathered by the module are made available via a
> >      view named <structname>pg_stat_statements</structname>.  This view
> > -   contains one row for each distinct database ID, user ID and query
> > -   ID (up to the maximum number of distinct statements that the module
> > +   contains one row for each distinct database ID, user ID, query ID and
> > +   toplevel (up to the maximum number of distinct statements that the module
> >      can track).  The columns of the view are shown in
> >      <xref linkend="pgstatstatements-columns"/>.
> 
> I'm having trouble parsing this new sentence.  It now says essentially
> 
> "This view contains one row for each distinct database ID, each distinct
> user ID, each distinct query ID, and each distinct toplevel."

Isn't it each distinct permutation of all those fields?

> That last part doesn't make sense.

I'm not sure what you mean by that.  Maybe it's not really self explanatory
without referring to what toplevel is, which is a bool flag stating whether the
statement was exected as a top level statement or not.

So every distinct permutation of (dbid, userid, queryid) can indeed be stored
twice, if pg_stat_statements.track is set to all.  However in practice most
statements are not executed both as top level and nested statements.

Commits

  1. Clarify description of pg_stat_statements columns

  2. Fix wording in description of pg_stat_statements.toplevel

  3. Mention that toplevel is part of pg_stat_statements key.

  4. adjust query id feature to use pg_stat_activity.query_id

  5. Update copyright for 2021

  6. Take the statistics collector out of the loop for monitoring backends'