mongoid_utils.rb

module MongoidUtils

  # Utility module to include in Mogoid documents
  module Document
    extend ActiveSupport::Concern

    module ClassMethods
      # Do a map/reduce operation on the document's collection and return the results as one big
      # hash. If a block is given, it is yielded with key and value for every result instead
      # (this comes in handy if you expect large results)
      def map_reduce (map_function, reduce_function, options = {})
        options[:query] = criteria.selector
        tmp_collection = criteria.klass.collection.map_reduce(map_function, reduce_function, options)
        if block_given?
          tmp_collection.find.each { |doc| yield doc['_id'], doc['value'] }
          nil
        else
          tmp_collection.find.to_a.inject({}) { |results, doc| results[doc['_id']] = doc['value']; results }
        end
      ensure
        tmp_collection.drop if tmp_collection
      end
      alias :mapreduce :map_reduce
    end
  end
end