Ron,
I've somehow missed part of this thread, which is a shame since this is
an area of primary concern for me.
Your suggested algorithm seems to be designed to relieve I/O load by
making more use of the CPU. (if I followed it correctly). However,
that's not PostgreSQL's problem; currently for us external sort is a
*CPU-bound* operation, half of which is value comparisons. (oprofiles
available if anyone cares)
So we need to look, instead, at algorithms which make better use of
work_mem to lower CPU activity, possibly even at the expense of I/O.
--Josh Berkus