| From: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> |
|---|---|
| To: | depesz(at)depesz(dot)com |
| Cc: | sathiya psql <sathiya(dot)psql(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: postgresql is slow with larger table even it is in RAM |
| Date: | 2008-03-25 09:34:35 |
| Message-ID: | 47E8C72B.2010105@postnewspapers.com.au |
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| Lists: | pgsql-performance |
hubert depesz lubaczewski wrote:
> On Tue, Mar 25, 2008 at 02:05:20PM +0530, sathiya psql wrote:
>> Any Idea on this ???
>
> yes. dont use count(*).
>
> if you want whole-table row count, use triggers to store the count.
>
> it will be slow. regeardless of whether it's in ram or on hdd.
In other words, if you're having performance problems please provide
EXPLAIN ANALYZE output from a more useful query that does real work,
rather than something like count(*).
COUNT(*) can be slow due to some MVCC limitations; it's been discussed
frequently here so you should search the archives for information.
--
Craig Ringer
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