has_many :bugs, :through => :rails: Thread safety for your Rails
http://m.onkey.org/2008/10/23/thread-safety-for-your-rails

Long story short, Rails can now serve multiple requests in more than one ruby threads ( or native threads if you’re on JRuby ) parallelly. Charles Nutter has done a good job of explaining the details here. Should you give a flying fuck ? You totally should if : * You’re using JRuby * You’re bold enough to play around with bleeding edge Neverblock stuff * Your application has a lot of long running processes, which are not heavy on blocking IO ( this would be rare I imagine ) You totally should NOT if : * You’re using Event based mongrel, thin or any of the event based web server in production. Event based servers don’t use Threads, so it just doesn’t matter. * You CBA You may have heard a bunch of hype about how threads make everything 100x faster, this is far from the truth. Don’t believe everything the hype merchants want to sell you, test your application first and see if it helps.