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From: Pierre C <lists@peufeu.com>
To: Nikolas Everett <nik9000@gmail.com>
Cc: Greg Smith <greg@2ndquadrant.com>
Cc: Dave Crooke <dcrooke@gmail.com>
Cc: Paul McGarry <paul@paulmcgarry.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: shared_buffers advice
Date: Tue, 16 Mar 2010 14:48:43 +0100
Message-ID: <op.u9nxzhryeorkce@localhost> (raw)
In-Reply-To: <d4e11e981003160626o6c76d902t16073cabb4dadabc@mail.gmail.com>
References: <a056b1d41003101728h2bfe964cg43bf5ef1aabae14d@mail.gmail.com>
	<ca24673e1003152217q117b0fd3q7d2d75ff20185c8b@mail.gmail.com>
	<4B9F3302.4020900@2ndquadrant.com>
	<op.u9nrbeeteorkce@localhost>
	<d4e11e981003160626o6c76d902t16073cabb4dadabc@mail.gmail.com>

> I think the logic you are referring to is the clock sweep buffer  
> accounting
> scheme.  That just makes sure that the most popular pages stay in the
> buffers.  If your entire db fits in the buffer pool then it'll all get in
> there real fast.


Actually, I meant that in the case of a seq scan, PG will try to use just  
a few buffers (a ring) in shared_buffers instead of thrashing the whole  
buffers. But if there was actually a lot of free space in shared_buffers,  
do the pages stay, or do they not ?

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