Thanks David and Jonathan! @David Yes rows doesn't have a name, I'm just using the word name for anything, like cluster name, table name, row name etc, that is my bad.
Yes, I did change two things, that was probably stupid, but the reason for the second change is space efficiency. You are totally right that I'm choosing between scalability and performance with the different structures. What I really want to do is to just store indices in rows with a composite key and do range queries. Jonathan has firmly steered me away from this approach for now in regards to performance. Thanks a lot! Erik