Interesting, in my database (http://root.rupy.se) I have one file per word that contains the ids (long) of the nodes (URLs), so to search many words together I have to go through the first file and one by one see if I find matches in the second.

How does the range binary search work, does it just prune out the overlaps, how efficient is it and how much data do you have in there for say "hello" and "world" f.ex?