Re: pg_buffercache's usage count

Greg Smith wrote:
> Ben Chobot wrote:
> >On Feb 23, 2010, at 3:06 PM, Ben Chobot wrote:
> >
> >>I'm looking at the usage count column of pg_buffercache's info, and I'm confused. Several buffers that supposed
haveLRU values of 5 belong to non-unique indices which supposedly have never been used. As I understand things, that
shouldn'thappen. Am I missing something? 
> >
> >(And maybe more to the point, when does the LRU go down in value?)
>
> Usage counts only go up when a page is "pinned" because some backend
> requested that particular block for its work via a call to
> BufferAlloc with the file/block it needs.

BTW the only reason you don't see buffers having a larger "usage" is
that the counters are capped at that value.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.