The query_reviewer, a classic Rails utility
I have been using the query_reviewer rails plugin since 2009. If you haven't used it, this is the time to take a look. I reviewed and applied all the fixes since into a compilation fork which also turns the utility into a gem. Used for development, this utility will analyze all SQL queries generated on a given page, run EXPLAIN on the slow ones, rate the severity of the various slow or inefficient queries and display that all within an easy to use panel on the top corner of the browser. Thanks Kongregate and David Stevenson for creating this.