Stef <svb(at)ucs(dot)co(dot)za> writes:
> => And what PG version is this, exactly?
> PostgreSQL 7.3.1
Ah, I think I see it: you are getting burnt by a mergejoin estimation
bug that was fixed in 7.3.2. Please update (you might as well go to
7.3.4 while you're at it) and see if the results improve.
regards, tom lane