Peter,
> Is it intentional that effective_cache_size is a real (as opposed to
> integer)? The initial revision of guc.c already has it that way, so it
> was probably blindly adapted from the previous adhockery that had all
> planner variables be doubles.
>
I beleive that it's a real because the other query estimate variables
are reals. Might be worth checking the estimation code to make sure
that changing the type won't break anything.
--Josh