Saxon

It seems the simpler formulation

saxon:stream(doc('uri')/*/*)/*

is working, but the equivalent verbose form

for $x in saxon:stream(doc('uri')/*/*)/* return $x

is not. The query compiles into

docOrder((("uri" ! (StreamInstr(., snapshot(child::element()/child::element())))) treat as node())/child::element())

which is not streamable because it contains a sort into document order. By contrast the simpler expression compiles to

(("uri" ! (StreamInstr(., snapshot(child::element()/child::element())))) treat as node())/child::element()

I have solved the problem by persuading DocumentSorter.optimize() to try a little harder to get rid of the sort into document order. Specifically, it recomputes the special properties of the operand expression if necessary to see whether it really does require sorting.

Patch applied in the Saxon 9.8.0.2 maintenance release