[doh]

I haven't check the code, but as few queries as possible is not always the best approach. I bet you guys spent a lot of time on the problem, but still very curious how you landed with this decision.

For the relation data, you should check out Hexastore [0] (essentially graph storage). It takes up much more space, but you can follow any paths of relationship and you can do it step by step instead of loading everything at once.

[0] http://www.vldb.org/pvldb/1/1453965.pdf