Re: Extended Prefetching using Asynchronous IO - proposal and patch

The patch is attached.
It is based on clone of today's 9.4dev source.
I have noticed that this source is
(not suprisingly) quite a moving target at present,
meaning that this patch becomes stale quite quickly.
So although this copy is fine for reviewing,
it may quite probably soon not be correct
for the current source tree.

As mentioned before,  if anyone wishes to try this feature out
on 9.3.4,   I will be making a patch for that soon
which I can supply on request.