I'm not sure it's cheap. What you suggest would result in a substantial increase in clog accesses, which means (1) more I/O and (2) more contention. Certainly it's worth experimenting with, but it's no guaranteed win.
It seems like there's a number of issues we could fix by making the CLOG more efficient somehow -- from the elimination of hint bits to the ability to freeze pages without writing them.
Not, of course, that I have any idea how to do that. -- -- Josh Berkus PostgreSQL Experts Inc. http://www.pgexperts.com -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers