marginalia

Attach comments to your ActiveRecord queries. By default, it adds the application, controller, and action names as a comment at the end of each query.

This helps when searching log files for queries, and seeing where slow queries came from.

For example, once enabled, your logs will look like:

Account Load (0.3ms)  SELECT `accounts`.* FROM `accounts` 
WHERE `accounts`.`queenbee_id` = 1234567890 
LIMIT 1 
/*application:BCX,controller:project_imports,action:show*/

You can also these query comments with a tool like pt-query-digest to automate identification of controllers and actions that are hotspots forslow queries.

This gem was created at 37signals. You can read more about how we use it on our blog.

This has been tested and used in production with both the mysql and mysql2 gems, tested on Rails 2.3.5 through 3.2-stable. Patches are welcome for other database adapters.

Installation

For Rails 3.x:

gem 'marginalia'

Then bundle, and that's it!

For Rails 2.x:

If using cached externals, add to your config/externals.yml file.

Or, if your prefer using config.gem, you can use:

config.gem 'marginalia'

Finally, if bundled, you'll need to manually run the initialization step in an initializer, e.g.:

# Gemfile
gem 'marginalia', :require => false

#config/initializers/marginalia.rb
require 'marginalia'
Marginalia::Railtie.insert

Customization

Optionally, you can set the application name shown in the log like so in an initializer (e.g. config/initializers/marginalia.rb):

Marginalia.application_name = "BCX"

For Rails 3 applications, the name will default to your Rails application name. For Rails 2 applications, "rails" is used as the default application name.

Contributing

Start by bundling and creating the test database:

bundle
rake db:create

Then, running rake will run the tests on both the mysql and mysql2 adapters:

rake