A way to read shelves quickly?

[zmason at gmail.com]

I have a collection of about 5M shelves, each consisting of string->int
mappings with on the order of 500 entries per shelf.  I want to iterate
through them rapidly and get the contents of each.  But calling items()
on each of them is slow - on the order of 1 or 2 seconds.  Is there any
way I can speed up this process?

thanks
Zach