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Subject: Re: track_planning causing performance regression
To: Julien Rouhaud <rjuju123@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, Peter Geoghegan <pg@bowt.ie>,
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From: Fujii Masao <masao.fujii@oss.nttdata.com>
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On 2021/06/30 0:12, Julien Rouhaud wrote:
>>         Enabling this parameter may incur a noticeable performance penalty,
>> -      especially when a fewer kinds of queries 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.
>>
>> It could say "identical structure" or "the same queryid" or "identical queryid".
> 
> I think we should try to reuse the previous formulation.  How about
> "statements with identical query structure"?

I'm fine with this. So what about the following diff? I added <structname> tag.

        <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 a fewer kinds of queries are executed on many
-      concurrent connections.
+      especially when statements with identical query structure are executed
+      by many concurrent connections which compete to update a small number of
+      <structname>pg_stat_statements</structname> entries.
        The default value is <literal>off</literal>.
        Only superusers can change this setting.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION