diff --git a/app/models/cost_query.rb b/app/models/cost_query.rb
index 307a620c40..b23e12fa48 100644
--- a/app/models/cost_query.rb
+++ b/app/models/cost_query.rb
@@ -1,3 +1,5 @@
+require 'report'
+
 class CostQuery < Report
   def_delegators :result, :real_costs
 
diff --git a/app/models/cost_query/filter.rb b/app/models/cost_query/filter.rb
index 56d5fd7e2a..c27e8278ac 100644
--- a/app/models/cost_query/filter.rb
+++ b/app/models/cost_query/filter.rb
@@ -1,6 +1,8 @@
 require "set"
 
 class CostQuery::Filter < Report::Filter
+  require_dependency 'cost_query/filter/base'
+
   def self.all
     @all ||= super + Set[
       CostQuery::Filter::ActivityId,
diff --git a/app/models/cost_query/group_by/singleton_value.rb b/app/models/cost_query/group_by/singleton_value.rb
deleted file mode 100644
index 38af901b3b..0000000000
--- a/app/models/cost_query/group_by/singleton_value.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-class CostQuery::GroupBy
-  class SingletonValue < CostQuery::GroupBy::Base
-    dont_display!
-  end
-end
-
diff --git a/app/models/cost_query/result.rb b/app/models/cost_query/result.rb
index df8b60c6dd..2f53b8ea84 100644
--- a/app/models/cost_query/result.rb
+++ b/app/models/cost_query/result.rb
@@ -1,5 +1,5 @@
 class CostQuery::Result < Report::Result
-  class Base < Report::Result::Base
+  module BaseAdditions
     def inspect
       "<##{self.class}: @fields=#{fields.inspect} @type=#{type.inspect} " \
       "@size=#{size} @count=#{count} @units=#{units} @real_costs=#{real_costs}>"
@@ -10,167 +10,29 @@ class CostQuery::Result < Report::Result
     end
   end
 
-  class DirectResult < Base
-    alias fields values
-
-    def has_children?
-      false
-    end
+  class Base < Report::Result::Base
+    include BaseAdditions
+  end
 
+  class DirectResult < Report::Result::DirectResult
+    include BaseAdditions
     def display_costs
       self["display_costs"].to_i
     end
 
-    def count
-      self["count"].to_i
-    end
-
-    def units
-      self["units"].to_d
-    end
-
     def real_costs
       (self["real_costs"] || 0).to_d if display_costs? # FIXME: default value here?
     end
-
-    ##
-    # @return [Integer] Number of child results
-    def size
-      0
-    end
-
-    def each
-      return enum_for(__method__) unless block_given?
-      yield self
-    end
-
-    def each_direct_result(cached = false)
-      return enum_for(__method__) unless block_given?
-      yield self
-    end
-
-    def sort!(force = false)
-      force
-    end
   end
 
-  class WrappedResult < Base
-    include Enumerable
-
-    def set_key(index = [])
-      values.each { |v| v.set_key index }
-      super
-    end
-
-    def sort!(force = false)
-      return false if @sorted and not force
-      values.sort! { |a,b| a.key <=> b.key }
-      values.each { |e| e.sort! force }
-      @sorted = true
-    end
-
-    def depth_of(type)
-      super + first.depth_of(type)
-    end
-
-    def has_children?
-      true
-    end
-
-    def count
-      sum_for :count
-    end
-
+  class WrappedResult < Report::Result::WrappedResult
+    include BaseAdditions
     def display_costs
       (sum_for :display_costs) >= 1 ? 1 : 0
     end
 
-    def units
-      sum_for :units
-    end
-
     def real_costs
       sum_for :real_costs if display_costs?
     end
-
-    def sum_for(field)
-      @sum_for ||= {}
-      @sum_for[field] ||= sum { |v| v.send(field) || 0 }
-    end
-
-    def recursive_each_with_level(level = 0, depth_first = true, &block)
-      if depth_first
-        super
-        each { |c| c.recursive_each_with_level(level + 1, depth_first, &block) }
-      else #width-first
-        to_evaluate = [self]
-        lvl = level
-        while !to_evaluate.empty? do
-          # evaluate all stored results and find the results we need to evaluate soon
-          to_evaluate_soon = []
-          to_evaluate.each do |r|
-            block.call(lvl,r)
-            to_evaluate_soon.concat r.values if r.size > 0
-          end
-          # take new results to evaluate
-          lvl = lvl +1
-          to_evaluate = to_evaluate_soon
-        end
-      end
-
-      def each_row
-        return enum_for(:each_row) unless block_given?
-        if final_row? then yield self
-        else each { |c| c.each_row(&Proc.new) }
-        end
-      end
-    end
-
-    def to_a
-      values
-    end
-
-    def each(&block)
-      values.each(&block)
-    end
-
-    def each_direct_result(cached = true)
-      return enum_for(__method__) unless block_given?
-      if @direct_results
-        @direct_results.each { |r| yield(r) }
-      else
-        values.each do |value|
-          value.each_direct_result(false) do |result|
-            (@direct_results ||= []) << result if cached
-            yield result
-          end
-        end
-      end
-    end
-
-    def fields
-      @fields ||= {}.with_indifferent_access
-    end
-
-    ##
-    # @return [Integer] Number of child results
-    def size
-      values.size
-    end
-  end
-
-  def self.new(value, fields = {}, type = nil, important_fields = [])
-    result = begin
-      case value
-      when Array then WrappedResult.new value.map { |e| new e, {}, nil, important_fields }
-      when Hash  then DirectResult.new value.with_indifferent_access
-      when Base  then value
-      else raise ArgumentError, "Cannot create Result from #{value.inspect}"
-      end
-    end
-    result.fields.merge! fields
-    result.type = type if type
-    result.important_fields = important_fields unless result == value
-    result
   end
 end