Sorting limits output in some cases

Supplying a sort parameter appears to break when the parameter can not be resolved to a value. This is because the sort parameter is joined using an inner join. The immediate conclusion is that switching to a left or outer join would solve the problem, which it will for N-1 type relationships, but as soon as we have a collection (N-N) relationship we end up with repeating results. This needs properly thinking about so as to not break existing behaviours.