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Re: URGENT HELP about 'duration' stats

From: Camilo Porto <camiloporto(at)hotmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: URGENT HELP about 'duration' stats
Date: 2007-10-27 14:10:06
Message-ID: BLU111-W4F245D9D14469DA3F8AA8BC970@phx.gbl (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers

[Camilo Porto]

> To: camiloporto(at)hotmail(dot)com
> CC: pgsql-hackers(at)postgresql(dot)org
> Subject: Re: [HACKERS] URGENT HELP about 'duration' stats 
> Date: Fri, 26 Oct 2007 23:06:22 -0400
> From: tgl(at)sss(dot)pgh(dot)pa(dot)us
> Camilo Porto <camiloporto(at)hotmail(dot)com> writes:
> > The problem I have encountered is that the sum of executor's
> > duration time is, *sometimes*, bigger than the total time interval in
> > which the statements had been executed!! And this makes no sense!
> Umm ... why not?  If you have, say, two queries executing in parallel
> for 1 second, they'll each report a duration: of 1 second, thus summing
> to 2 seconds, but the elapsed time was only 1 second.
> If you don't see that always, then your benchmark program isn't trying
> very hard to run more than one query in parallel ...

This really make sense, but let me add some questions:

The parallelism happens even if my PC has only one processor? 
Each query is executed in a separeted Thread? 
I am simulating only 1 client with the Benchmark. Can 1 Client submit parallel queries, in single-processor enviroment?

Many Thanks
> 			regards, tom lane

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