"Steven Flatt" <steven(dot)flatt(at)gmail(dot)com> writes:
> Regarding your other email -- interesting -- but we are vacuuming pg_class
> every hour. So I don't think the answer lies there...
That's good, but is the vacuum actually accomplishing anything? I'm
wondering if there's also a long-running transaction in the mix.
Try a manual "VACUUM VERBOSE pg_class;" after the thing has slowed down,
and see what it says about removable and nonremovable rows.
regards, tom lane