ctid ranges

Hi

In 9.1.3, this is fast, handled with a tid scan using the physical address:

SELECT ... FROM ... WHERE ctid = ...;

This is slow, handled with a seq scan (as are various rephrasing with
<, <=, etc):

SELECT ... FROM ... WHERE ctid BETWEEN ... AND ...;

Is there a way to retrieve the rows in a physical range quickly?

(I realise this is a pretty odd thing to want to do... I was
experimenting with a crackpot idea for storing some data in a known
physical order and finding the beginning of ends ranges by binary
chop, instead of using a btree.)

Thanks
Thomas Munro