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Re: VACUUM and spoiling the buffer manager cache

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: VACUUM and spoiling the buffer manager cache
Date: 2007-03-01 02:00:36
Message-ID: 20070301105503.5EA4.ITAGAKI.TAKAHIRO@oss.ntt.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers
"Simon Riggs" <simon(at)2ndquadrant(dot)com> wrote:

> > > VACUUM's current behaviour is to take blocks it has touched and place
> > > them on the head of the freelist, allowing them to be reused.
> > 
> > No, it puts them at the tail of the freelist.
> 
> That's a minor point because the freelist is mostly empty, so head ==
> tail in 99.9% of cases.

That's correct. Also, even if a VACUUM process collects some unused buffers
into the freelist, other backends comsume all of them in a moment.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center



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