Обсуждение: Can Postgres cache a table in memory?

Hello all;

I'm trying to speed up a query which returns the majority of a table so and
index isn't helpful.
I've got more than enough RAM to hold my table so, can anyone tell me if
there is there a way to force Postgres to cache a table in RAM?

Any help would be appreciated.

Thanks;
-Kevin Traub

On Thu, 3 Oct 2002, Kevin Traub wrote:

> Hello all;
>
> I'm trying to speed up a query which returns the majority of a table so and
> index isn't helpful.
> I've got more than enough RAM to hold my table so, can anyone tell me if
> there is there a way to force Postgres to cache a table in RAM?
>
> Any help would be appreciated.

You need to tune first of all shared_buffers.
Change the postgres.conf file usual in $PGDATA directory.
Bare in mind that one buffer holds 8k of data.


>
> Thanks;
> -Kevin Traub
>
>
>
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On Thursday 03 Oct 2002 3:03 pm, Kevin Traub wrote:
> Hello all;
>
> I'm trying to speed up a query which returns the majority of a table so and
> index isn't helpful.
> I've got more than enough RAM to hold my table so, can anyone tell me if
> there is there a way to force Postgres to cache a table in RAM?

You're probably just as well off if you let your OS deal with caching the
underlying file. What figures are you getting (use the "free" command if in
linux). It might be that you've given Postgresql *too* much memory, and
that's interfering with your OS.

Could you provide brief hardware specs, the size of the table concerned, time
taken?

--  Richard Huxton

"Kevin Traub" <ktraub@verizon.net> writes:
> I'm trying to speed up a query which returns the majority of a table so and
> index isn't helpful.
> I've got more than enough RAM to hold my table so, can anyone tell me if
> there is there a way to force Postgres to cache a table in RAM?

There is no need to do anything; if you're hitting the table a lot, it
should all migrate into kernel disk buffers.
        regards, tom lane

Kevin,

> I'm trying to speed up a query which returns the majority of a table
> so and
> index isn't helpful.
> I've got more than enough RAM to hold my table so, can anyone tell me
> if
> there is there a way to force Postgres to cache a table in RAM?

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-Josh Berkus