| From: | Jon Nelson <jnelson+pgsql(at)jamponi(dot)net> |
|---|---|
| To: | mladen(dot)gogala(at)vmsinfo(dot)com |
| Cc: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, Neil Whelchel <neil(dot)whelchel(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Slow count(*) again... |
| Date: | 2010-10-10 22:50:22 |
| Message-ID: | AANLkTi=gbaApWtgDEwH0A_tyjVroqMzaGEaqvjPKpCpO@mail.gmail.com |
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| Lists: | pgsql-hackers pgsql-performance |
On Sun, Oct 10, 2010 at 12:14 PM, Mladen Gogala
<mladen(dot)gogala(at)vmsinfo(dot)com> wrote:
>
>
>
> In other words, when I batched the sequential scan to do 128 blocks I/O, it
> was 4 times faster than when I did the single block I/O.
> Does that provide enough of an evidence and, if not, why not?
These numbers tell us nothing because, unless you dropped the caches
between runs, then at least part of some runs was very probably
cached.
--
Jon
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