Re: pg_buffercache description

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.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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