| From: | Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Slow count(*) again... |
| Date: | 2010-10-13 08:44:09 |
| Message-ID: | 4CB57159.2090501@vmsinfo.com |
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| Lists: | pgsql-hackers pgsql-performance |
On 10/13/2010 3:19 AM, Mark Kirkwood wrote:
> I think that major effect you are seeing here is that the UPDATE has
> made the table twice as big on disk (even after VACUUM etc), and it has
> gone from fitting in ram to not fitting in ram - so cannot be
> effectively cached anymore.
>
In the real world, tables are larger than the available memory. I have
tables of several hundred gigabytes in size. Tables shouldn't be
"effectively cached", the next step would be to measure "buffer cache
hit ratio", tables should be effectively used.
--
Mladen Gogala
Sr. Oracle DBA
1500 Broadway
New York, NY 10036
(212) 329-5251
www.vmsinfo.com
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