Re: pg_buffercache description

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 <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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