Re: WIP: explain analyze with 'rows' but not timing

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Tomas Vondra <tv(at)fuzzy(dot)cz>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: WIP: explain analyze with 'rows' but not timing
Date: 2011-12-24 05:31:31
Message-ID: CAFj8pRCdHvm0zv3i2JDrA-Rt+nddGiiSUNapCHc-=7WPFTL3pA@mail.gmail.com
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2011/12/23 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> 2011/12/23 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>>> Tomas Vondra <tv(at)fuzzy(dot)cz> writes:
>>>> The motivation for this patch was that collection timing data often
>>>> causes performance issues and in some cases it's not needed. But is this
>>>> true for row counts?
>
>>> Perhaps more to the point, is there a use case for collecting timing
>>> data without row counts?  I find it hard to visualize a valid reason.
>
>> yes - a searching of bad prediction
>
> No, because timing alone proves nothing at all.  The machine could just
> have been overloaded.

sorry, I didn't understand to question.

Using only time is not practical

Regards

Pavel

>
>                        regards, tom lane

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