Bullet: An Eager Loading Adviser Plugin
Bullet is a new Rails plugin (developed by Richard Huang) that helps you reduce the number of queries your Rails app makes, thus increasing its performance.
Essentially, Bullet "watches" the queries your Rails app makes through ActiveRecord and notifies you as to where you should add eager loading or where eager loading is being taking place but not providing any benefits (so you can disable it). It's advised you run Bullet only in development mode while you're working on the app as it's principally for the developer's use.
Bullet's README goes into detail on its operation. By default it does nothing, so you have some options to turn on to get the effect you want.
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