MongoDB Tree MapReduce

path-tree-map-reduce.rb

# Encoding: UTF-8

# This defined a way to do a Map/Reduce search
# in MongoDB to find all service groups that has
# a given device in either the TX or RX path tree.
module ServiceGroupPathSearch
  extend ActiveSupport::Concern

  included do
    class_eval do
      def self.path_search(node)
        mfunc = path_search_map
        rfunc = path_search_reduce
        args  = { out: 'path_search', scope: { search_name: node.name } }

        cursor = self.collection.map_reduce(mfunc, rfunc, args).find()

        find cursor.first['value']['ids']
      end

      def self.path_search_map
        <<-MAP
          function mapFunc() {
            function hasName(path) {
              if (path.name == search_name) return true;
              if (!path.children || !path.children.length) return false;

              for (var idx = 0; idx < path.children.length; idx++) {
                good = hasName(path.children[idx]);

                if (good) return true;
              }

              return false;
            }

            if (hasName(this.tx) || hasName(this.rx)) {
              emit('paths', { id: this._id });
            }
          }
        MAP
      end

      def self.path_search_reduce
        <<-REDUCE
          function reduceFunc(id, values) {
            var data = { ids: [] };

            for (idx in values) {
              data.ids.push(values[idx].id)
            }

            return data;
          }
        REDUCE
      end
    end
  end
end