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Re: postgresql is slow with larger table even it is in RAM

From: Elvis Henríquez <henriquez(dot)elvis(at)gmail(dot)com>
To: "sathiya psql" <sathiya(dot)psql(at)gmail(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: postgresql is slow with larger table even it is in RAM
Date: 2008-03-27 10:35:40
Message-ID: 493343bd0803270335i59c2ba65yded0a1c11982b384@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-admin
We could notice your processor is an Intel Celeron. They have a small cache,
as you can see for yourself in your output.

But, what about postgresql.conf ? How many memory resources are being
assigned in your configuration?

If you only have 1.25 GB of RAM and you're creating a tablespace in RAM
which holds a table about 0.8 GB in size, and have created indexes in the
same tablespace in RAM, you could be getting out of RAM. vmstat says you're
not using swap, but if you leave the postgresql process only ~100 MB of RAM,
it surely will have a bad performance.

Once the server is up and running, which is the output of free ?

Which tool are you using to retrieve data ? psql is pretty much faster than
phpPgAdmin and this one is faster than pgAdmin.

Elvis E. Henríquez A.

On Wed, Mar 26, 2008 at 4:18 AM, sathiya psql <sathiya(dot)psql(at)gmail(dot)com>
wrote:

>
>
> On Tue, Mar 25, 2008 at 2:11 PM, CZUCZY Gergely <
> gergely(dot)czuczy(at)harmless(dot)hu> wrote:
>
> > May I ask, do you have any indeces or a primary key on that table?
> >
> yes, i have both the index and primary key on a column "id",
> and am doing the
>
> SELECT count(id) from TABLE;
>
> this is taking 3 seconds
>

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