How to get highest count of associated model (Rails)?

Question

A User has_many Solutions

How do I order Users by those with the most Solutions?

I'm trying to find the top ten users but I'm not sure how the most tidy or efficient way to do this?

Does anyone have an example that isn't too computationally expensive?

Answer 1

If you really want a fast way of doing it, put a counter_cache on a users' solutions (have a solutions_count column in your User) and order by that column. You don't need to manage that counter, because rails does it for you. You can read more about counter_cache in the Rails Guides