It's nice that ActiveRecord logs the queries that are performed when your actions are executed, since it makes it easy to see when you have serious inefficiencies in your application. The next question, though, is always, "OK, so where are those being run from?" Before QueryTrace, that question could be a real pain to answer, since you'd have to go trawling through your code looking for the culprit. Once you have QueryTrace installed, though, your logs won't just tell you that you have a problem, they will pinpoint the location of that problem for you.