Ruby on Rails – your own slow query log, no sql configuration required

slow_query_logger.rb

# http://pdabrowski.com/blog/ruby-on-rails/slow-query-log/
# config/initializer/slow_query_logger.rb

class SlowQueryLogger
  MAX_DURATION = 3.0

  def self.initialize!
    ActiveSupport::Notifications.subscribe('sql.active_record') do |name, start, finish, id, payload|
      duration = finish.to_f - start.to_f

      if duration >= MAX_DURATION
        SomeLogger.log("slow query detected: #{payload[:sql]}, duration: #{duration}")
      end
    end
  end
end

SlowQueryLogger.initialize!