Attached is a patch that avoids a needless copy of the result tuple in
nodeMaterial, in the case that we don't have a previously-materialized
tuple to return. We can just return the TTS produced by executing our
child node, rather than returning a copy of it.
I didn't bother pulling the MinimalTuple out of "outerslot" and stuffing
it back into the nodeMaterial's result slot, as AFAICS that is not
necessary. Although I suppose you could make a cleanliness argument that
that would be worth doing instead.
(This is 8.4 material...)
-Neil