It took me a while to work out how to use map-reduce in Ruby using mongoid so I thought I’d share it here in-case it helps anyone else get there quicker. I start out with a model that includes Mongoid::Document:
To map-reduce across the collection I need to define a map and reduce function in javascript then run the on the collection:
I can roll this into my VisitorSession model:
This obviously makes it easier to call:
>> VisitorSession.first(:conditions => {:project_id => '2f5178'}).visits_for_project
=> 1
