| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | sathiya psql <sathiya(dot)psql(at)gmail(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: postgresql is slow with larger table even it is in RAM |
| Date: | 2008-03-25 11:59:21 |
| Message-ID: | 20080325115921.GB6756@alvh.no-ip.org |
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| Lists: | pgsql-performance |
sathiya psql escribió:
> So now everything is in RAM, if i do a count(*) on this table it returns
> 327600 in 3 seconds, why it is taking 3 seconds ????? because am sure that
> no Disk I/O is happening.
It has to scan every page and examine visibility for every record. Even
if there's no I/O involved, there's a lot of work to do. I am not sure
if with your hardware it is expected for it to take 3 seconds though.
Do you see high CPU usage during that period?
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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