On Fri, Jan 2, 2009 at 17:22, Tom Lane <t...@sss.pgh.pa.us> wrote: > A couple of other possibilities that seem a bit saner: > > 1. Use a self-organizing list: any time an entry is referenced, > move it to front, and when you need a new entry take the oldest > one off the back. I don't see a way to do that without a global > lock that protects the list links, but there could be a spinlock > that's held only long enough to manipulate the list links. > > 2. Use a clock sweep algorithm similar to bufmgr's. > > Either of these trades off accuracy of deciding which existing cache > entries are "least interesting" in order to reduce the maintenance > overhead --- but it doesn't appear to me that the code implements usage > counts in a way that would justify treating them as sacrosanct > indicators of relative usefulness anyhow. > > The first option seems attractively simple and predictable in > performance --- all operations are O(1).
Its seems to me a linear list would make the "common" case where the query is already in the list but we need to update the stats slow. Or am I just thinking to abstractly and the list is not a pg_list.h list but just a c array and use a simple hash. (or I guess we could "hash" and the use list_nth_cel()... but that *seems* slow)? -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
