Good examples of Rails model designs for complex and interesting problems

I need to "step my game up" :D when it comes to writing complex models. Currently 开发者_开发技巧I got a bunch of theory, I have read Agile Web Development with Rails, also Rails Guides, RailsCasts and so on... but every time I need to write something a bit more complex I just end up writing pure SQL (which I know isn't bad in some cases).

So is there any good resources from which I could learn how smart guys solve difficult database problems beautifully?

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A good idea might be looking into NoSQL - it's a different perspective on doing things.

I'd recommend http://guide.couchdb.org/ - a reasonably good read.

Also to make you awesome with ActiveRecord and Ruby - read the ActiveRecord source. You'll probably learn a lot from there.