Re: How does PG know if data is in memory?

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: Fabrício dos Anjos Silva <fabricio(dot)silva(at)linkcom(dot)com(dot)br>, <pgsql-performance(at)postgresql(dot)org>
Subject: Re: How does PG know if data is in memory?
Date: 2010-09-29 16:36:45
Message-ID: 4CA324CD0200002500036117@gw.wicourts.gov
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Fabrício dos Anjos Silva<fabricio(dot)silva(at)linkcom(dot)com(dot)br> wrote:

> After reading lots of documentation, I still don't understand
> fully how PG knows if some needed data is in memory or in second
> storage.

> Does PG consider this?

No.

> When setting seq_page_cost and random_page_cost, do I have to
> consider the probability that data will be in memory?

Yes.

-Kevin

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