1 files changed, 25 insertions, 8 deletions
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_part.rb b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
index 8024105472..d39ce94c99 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_part.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_part.rb
@@ -8,25 +8,42 @@ module ActiveRecord
       # operations (for example a has_and_belongs_to_many JoinAssociation would result in
       # two; one for the join table and one for the target table).
       class JoinPart # :nodoc:
+        include Enumerable
+
+        # A JoinBase instance representing the active record we are joining onto.
+        # (So in Author.has_many :posts, the Author would be that base record.)
+        attr_reader :parent
+
         # The Active Record class which this join part is associated 'about'; for a JoinBase
         # this is the actual base model, for a JoinAssociation this is the target model of the
         # association.
-        attr_reader :base_klass
+        attr_reader :base_klass, :children
 
-        delegate :table_name, :column_names, :primary_key, :reflections, :arel_engine, :to => :base_klass
+        delegate :table_name, :column_names, :primary_key, :arel_engine, :to => :base_klass
 
-        def initialize(base_klass)
+        def initialize(base_klass, parent)
           @base_klass = base_klass
+          @parent = parent
           @cached_record = {}
           @column_names_with_alias = nil
+          @children = []
         end
 
-        def aliased_table
-          Arel::Nodes::TableAlias.new table, aliased_table_name
+        def name
+          reflection.name
         end
 
-        def ==(other)
-          raise NotImplementedError
+        def match?(other)
+          self.class == other.class
+        end
+
+        def each(&block)
+          yield self
+          children.each { |child| child.each(&block) }
+        end
+
+        def aliased_table
+          Arel::Nodes::TableAlias.new table, aliased_table_name
         end
 
         # An Arel::Table for the active_record
@@ -54,7 +71,7 @@ module ActiveRecord
           unless @column_names_with_alias
             @column_names_with_alias = []
 
-            ([primary_key] + (column_names - [primary_key])).compact.each_with_index do |column_name, i|
+            column_names.each_with_index do |column_name, i|
               @column_names_with_alias << [column_name, "#{aliased_prefix}_r#{i}"]
             end
           end