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Date: Fri, 20 Jan 2023 07:43:00 +0100
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Subject: Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?
From: David Geier <geidav.pg@gmail.com>
To: Pavel Stehule <pavel.stehule@gmail.com>,
 Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: vignesh C <vignesh21@gmail.com>, Lukas Fittl <lukas@fittl.com>,
 Michael Paquier <michael@paquier.xyz>, Ibrar Ahmed <ibrar.ahmad@gmail.com>,
 Maciek Sakrejda <m.sakrejda@gmail.com>, Andres Freund <andres@anarazel.de>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
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On 1/18/23 13:52, David Geier wrote:
> On 1/16/23 21:39, Pavel Stehule wrote:
>>
>> po 16. 1. 2023 v 21:34 odesílatel Tomas Vondra 
>> <tomas.vondra@enterprisedb.com> napsal:
>>
>>     Hi,
>>
>>     there's minor bitrot in the Mkvcbuild.pm change, making cfbot 
>> unhappy.
>>
>>     As for the patch, I don't have much comments. I'm wondering if 
>> it'd be
>>     useful to indicate which timing source was actually used for EXPLAIN
>>     ANALYZE, say something like:
>>
>>      Planning time: 0.197 ms
>>      Execution time: 0.225 ms
>>      Timing source: clock_gettime (or tsc)
>>
>> +1
>
> I like the idea of exposing the timing source in the EXPLAIN ANALYZE 
> output.
> It's a good tradeoff between inspectability and effort, given that 
> RDTSC should always be better to use.
> If there are no objections I go this way.
Thinking about this a little more made me realize that this will cause 
different pg_regress output depending on the platform. So if we go this 
route we would at least need an option for EXPLAIN ANALYZE to disable 
it. Or rather have it disabled by default and allow for enabling it. 
Thoughts?

-- 
David Geier
(ServiceNow)