From: Justin Pryzby <pryzby@telsasoft.com>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Peter Geoghegan <pg@bowt.ie>
Cc: Julien Rouhaud <rjuju123@gmail.com>
Cc: Tharakan, Robins <tharar@amazon.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: track_planning causing performance regression
Date: Mon, 28 Jun 2021 21:09:18 -0500
Message-ID: <20210629020918.GE21248@telsasoft.com> (raw)
In-Reply-To: <20210421154007.GU7256@telsasoft.com>
References: <bc8125cb-264e-5a48-7d1f-17b84df831ed@oss.nttdata.com>
<CAFj8pRC9Jxa8r5i0TNBWLb8mzuaYzEoLq3QOvip0jVpHPOLbVA@mail.gmail.com>
<646e5cae-5e8b-feaa-43dc-014bf355bf08@oss.nttdata.com>
<20210418233615.GB7256@telsasoft.com>
<d4cb31e2-d43f-0811-8f10-cf8e2f052e5e@oss.nttdata.com>
<20210419145545.GF7256@telsasoft.com>
<b86e33bf-d549-db6b-f50b-3cb077807a71@oss.nttdata.com>
<20210421145338.GT7256@telsasoft.com>
<f2aa2d6a-3b78-0526-4ca5-8ace10eb745e@oss.nttdata.com>
<20210421154007.GU7256@telsasoft.com>
On Wed, Apr 21, 2021 at 10:40:07AM -0500, Justin Pryzby wrote:
> On Thu, Apr 22, 2021 at 12:13:17AM +0900, Fujii Masao wrote:
> > On 2021/04/21 23:53, Justin Pryzby wrote:
> > > Or:
> > >
> > > Enabling this parameter may incur a noticeable performance penalty,
> > > especially similar queries are executed by many concurrent connections
> > > and compete to update a small number of pg_stat_statements entries.
> >
> > I prefer this. But what about using "identical" instead of "similar"
> > because pg_stat_statements docs already uses "identical" in some places?
>
> I also missed "when", again...
>
> > > Enabling this parameter may incur a noticeable performance penalty,
> > > especially when queries with identical structure are executed by many concurrent connections
> > > which compete to update a small number of pg_stat_statements entries.
Checking back - here's the latest patch.
inline patch 1: doc/src/sgml/pgstatstatements.sgml (+3/-2 lines) download inline-1.patchdiff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgmlindex 930081c429..9e98472c5c 100644--- a/doc/src/sgml/pgstatstatements.sgml+++ b/doc/src/sgml/pgstatstatements.sgml@@ -696,8 +696,9 @@
<varname>pg_stat_statements.track_planning</varname> controls whether
planning operations and duration are tracked by the module.
Enabling this parameter may incur a noticeable performance penalty,
- especially when queries with the same queryid are executed on many- concurrent connections.+ especially when queries with identical structure are executed by many+ concurrent connections which compete to update a small number of+ pg_stat_statements entries.
The default value is <literal>off</literal>.
Only superusers can change this setting.
</para>
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To: pgsql-hackers@postgresql.org
Cc: pryzby@telsasoft.com, masao.fujii@oss.nttdata.com, pavel.stehule@gmail.com, pg@bowt.ie, rjuju123@gmail.com, tharar@amazon.com
Subject: Re: track_planning causing performance regression
In-Reply-To: <20210629020918.GE21248@telsasoft.com>
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