"Jim C. Nasby" <jnasby@pervasive.com> writes:
> But do fewer/longer sorted runs translate into not merging back to disk?
> I thought that was controlled by if we had to be able to rewind the
> result set.
A plain SELECT ... ORDER BY doesn't assume that anymore. It is still
required for some cases such as the input to a merge join, but the
on-the-fly-final-merge code is going to be used a lot more in 8.2 than
it was before.
regards, tom lane