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?
Regards,
--
Satoshi Nagayasu <snaga(at)uptime(dot)jp>
Uptime Technologies, LLC. http://www.uptime.jp