I'm writing bug-tracking software in Ruby using Sinatra and MongoMapper. The problem is that the ticket IDs aren't very user friendly; they are composed of 24 hexadecimal digits (e.g. `4fcfa9e1c3e7f20bc2000004`). I would like that the ticket IDs start at 1 and automatically increment (i.e. 1, 2, 3…). In MySQL this would be done using `AUTO_INCREMENT`.

I'm using MongoMapper, however. Is there a way to make the IDs start at 1 and then auto-increment, or do I need to store them *separately*?