> Right, but it seems to work without sorting in reduce if descending is > true. Although haven't tested on larger data set. > I would like to know if I can omit sorting entirely in this case with > same result, that is: > > For: reduce (null, [key_range_A1_A2, key_range_B1_B2, key_range_C1_C2], true) > Does the relation A1 < A2 < B1 < B2 < C1 < C2 hold? Does it depend on > descending? > > For: reduce ([k1,k2,k3], [v1,v2,v3], false) > Can I depend on k1 < k2 < k3 if descending=true? These are specifically the assertions I'm saying you can't rely on. In your case you will absolutely need to sort the input data. The only assumption I think its possible to make is that re-reductions will always process reductions from contiguous parts of the b+tree. I'm only at the *think* stage of certainty. I haven't gone through the implementation to check if that's an absolute truth, and I can't yet guarantee that it won't ever change if it is true. Just in case that doesn't make sense, imagine you have a set of reductions that are from ordered regions of the view b+tree labeled as such: A, B, C, D. That is to say, data in the reduction A is based entirely of keys <= reduction keys in B <= reduction keys in C <= reduction keys in D. Given that, the only assumption I think is possible is that you are guaranteed that if A and C are passed simultaneously to a re-reduce, then B is guaranteed to be passed as well. In other words, you wont get a reduction graph that looks like ((A | C) | (B | D)) which would break this sort of approach.