Christopher Browne <cbbrowne@gmail.com> writes:
> I picked values that I knew could be easily grabbed, and we don't
> have an immediate tuples-per-page estimate on pg_class.
Er, what? reltuples/relpages is exactly that estimate --- in fact,
it's only because of historical accident that we don't store a single
float field with that ratio, rather than two fields. Both the creation
and the usage of those numbers work explicitly with the ratio.
regards, tom lane