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From: Bruce Momjian <[email protected]>
To: Satoshi Nagayasu <[email protected]>
Cc: [email protected]
Subject: Re: pg_buffercache description
Date: Wed, 3 Jul 2013 14:26:36 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Wed, Jul  3, 2013 at 02:23:11PM -0400, Bruce Momjian wrote:
> On Sat, Nov 24, 2012 at 11:57:51AM +0900, Satoshi Nagayasu wrote:
> > Hi,
> > 
> > I found that the manual page for pg_buffercache module explains
> > "usagecount" as "Page LRU count".
> > 
> > http://www.postgresql.org/docs/devel/static/pgbuffercache.html
> > 
> > However, AFAIK, "usagecount" is not a LRU count nowadays, because
> > LRU is no longer used for the buffer management algorithm.
> > 
> > I think it should be described as "Clock-sweep count" or something
> > like that.
> > 
> > And I'd like to add some additional explanation for the "forknumber"
> > as below:
> > 
> > "0 for heap file, 1 for FreeSpaceMap, and 2 for VisibilityMap".
> > 
> > Any comments?
> 
> Good suggestion.  I ended up referencing the C file that contains the
> "forknumber" definitions, rather than recreating the list in the docs. 
> I applied the attached patch to head and 9.3.

I ended up applying it to 9.2 as well.

-- 
  Bruce Momjian  <[email protected]>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +


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