does datascript allow constraints of the form across all entities, :type/name must be unique thus, I can't ahve {:db/id 20, :type/name :vec2 .... } {:db/id 30, :type/name :vec2, ...} ?

@tonsky Would it be a good idea to add ICounted to btset/Iter? With:

(loop [cnt 0
         iter iter]
    (if iter
      (recur (+ cnt (-count (btset/iter-chunk iter))) (btset/iter-chunked-next iter))
      cnt))