breaking classes up in to respective files

5 files changed, 605 insertions, 574 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 7da38cd03f..0d9171d876 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -5,6 +5,7 @@ require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/string/conversions'
 require 'active_support/core_ext/module/remove_method'
 require 'active_support/core_ext/class/attribute'
+require 'active_record/associations/class_methods/join_dependency'
 
 module ActiveRecord
   class InverseOfAssociationNotFoundError < ActiveRecordError #:nodoc:
@@ -1832,580 +1833,6 @@ module ActiveRecord
             Array.wrap(extensions)
           end
         end
-
-        class JoinDependency # :nodoc:
-          attr_reader :join_parts, :reflections, :table_aliases
-
-          def initialize(base, associations, joins)
-            @join_parts            = [JoinBase.new(base, joins)]
-            @associations          = {}
-            @reflections           = []
-            @table_aliases         = Hash.new(0)
-            @table_aliases[base.table_name] = 1
-            build(associations)
-          end
-
-          def graft(*associations)
-            associations.each do |association|
-              join_associations.detect {|a| association == a} ||
-              build(association.reflection.name, association.find_parent_in(self) || join_base, association.join_type)
-            end
-            self
-          end
-
-          def join_associations
-            join_parts.last(join_parts.length - 1)
-          end
-
-          def join_base
-            join_parts.first
-          end
-
-          def count_aliases_from_table_joins(name)
-            # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
-            quoted_name = join_base.active_record.connection.quote_table_name(name.downcase).downcase
-            join_sql = join_base.table_joins.to_s.downcase
-            join_sql.blank? ? 0 :
-              # Table names
-              join_sql.scan(/join(?:\s+\w+)?\s+#{quoted_name}\son/).size +
-              # Table aliases
-              join_sql.scan(/join(?:\s+\w+)?\s+\S+\s+#{quoted_name}\son/).size
-          end
-
-          def instantiate(rows)
-            primary_key = join_base.aliased_primary_key
-            parents = {}
-
-            records = rows.map { |model|
-              primary_id = model[primary_key]
-              parent = parents[primary_id] ||= join_base.instantiate(model)
-              construct(parent, @associations, join_associations.dup, model)
-              parent
-            }.uniq
-
-            remove_duplicate_results!(join_base.active_record, records, @associations)
-            records
-          end
-
-          def remove_duplicate_results!(base, records, associations)
-            case associations
-              when Symbol, String
-                reflection = base.reflections[associations]
-                remove_uniq_by_reflection(reflection, records)
-              when Array
-                associations.each do |association|
-                  remove_duplicate_results!(base, records, association)
-                end
-              when Hash
-                associations.keys.each do |name|
-                  reflection = base.reflections[name]
-                  remove_uniq_by_reflection(reflection, records)
-
-                  parent_records = []
-                  records.each do |record|
-                    if descendant = record.send(reflection.name)
-                      if reflection.collection?
-                        parent_records.concat descendant.target.uniq
-                      else
-                        parent_records << descendant
-                      end
-                    end
-                  end
-
-                  remove_duplicate_results!(reflection.klass, parent_records, associations[name]) unless parent_records.empty?
-                end
-            end
-          end
-
-          protected
-
-            def cache_joined_association(association)
-              associations = []
-              parent = association.parent
-              while parent != join_base
-                associations.unshift(parent.reflection.name)
-                parent = parent.parent
-              end
-              ref = @associations
-              associations.each do |key|
-                ref = ref[key]
-              end
-              ref[association.reflection.name] ||= {}
-            end
-
-            def build(associations, parent = nil, join_type = Arel::InnerJoin)
-              parent ||= join_parts.last
-              case associations
-                when Symbol, String
-                  reflection = parent.reflections[associations.to_s.intern] or
-                  raise ConfigurationError, "Association named '#{ associations }' was not found; perhaps you misspelled it?"
-                  unless join_association = find_join_association(reflection, parent)
-                    @reflections << reflection
-                    join_association = build_join_association(reflection, parent)
-                    join_association.join_type = join_type
-                    @join_parts << join_association
-                    cache_joined_association(join_association)
-                  end
-                  join_association
-                when Array
-                  associations.each do |association|
-                    build(association, parent, join_type)
-                  end
-                when Hash
-                  associations.keys.sort{|a,b|a.to_s<=>b.to_s}.each do |name|
-                    join_association = build(name, parent, join_type)
-                    build(associations[name], join_association, join_type)
-                  end
-                else
-                  raise ConfigurationError, associations.inspect
-              end
-            end
-
-            def find_join_association(name_or_reflection, parent)
-              if String === name_or_reflection
-                name_or_reflection = name_or_reflection.to_sym
-              end
-
-              join_associations.detect { |j|
-                j.reflection == name_or_reflection && j.parent == parent
-              }
-            end
-
-            def remove_uniq_by_reflection(reflection, records)
-              if reflection && reflection.collection?
-                records.each { |record| record.send(reflection.name).target.uniq! }
-              end
-            end
-
-            def build_join_association(reflection, parent)
-              JoinAssociation.new(reflection, self, parent)
-            end
-
-            def construct(parent, associations, join_parts, row)
-              case associations
-              when Symbol, String
-                name = associations.to_s
-
-                join_part = join_parts.detect { |j|
-                  j.reflection.name.to_s == name &&
-                  j.parent_table_name    == parent.class.table_name }
-
-                raise(ConfigurationError, "No such association") unless join_part
-
-                join_parts.delete(join_part)
-                construct_association(parent, join_part, row)
-              when Array
-                associations.each do |association|
-                  construct(parent, association, join_parts, row)
-                end
-              when Hash
-                associations.sort_by { |k,_| k.to_s }.each do |name, assoc|
-                  association = construct(parent, name, join_parts, row)
-                  construct(association, assoc, join_parts, row) if association
-                end
-              else
-                raise ConfigurationError, associations.inspect
-              end
-            end
-
-            def construct_association(record, join_part, row)
-              return if record.id.to_s != join_part.parent.record_id(row).to_s
-
-              macro = join_part.reflection.macro
-              if macro == :has_one
-                return if record.instance_variable_defined?("@#{join_part.reflection.name}")
-                association = join_part.instantiate(row) unless row[join_part.aliased_primary_key].nil?
-                set_target_and_inverse(join_part, association, record)
-              else
-                return if row[join_part.aliased_primary_key].nil?
-                association = join_part.instantiate(row)
-                case macro
-                when :has_many, :has_and_belongs_to_many
-                  collection = record.send(join_part.reflection.name)
-                  collection.loaded
-                  collection.target.push(association)
-                  collection.__send__(:set_inverse_instance, association, record)
-                when :belongs_to
-                  set_target_and_inverse(join_part, association, record)
-                else
-                  raise ConfigurationError, "unknown macro: #{join_part.reflection.macro}"
-                end
-              end
-              association
-            end
-
-            def set_target_and_inverse(join_part, association, record)
-              association_proxy = record.send("set_#{join_part.reflection.name}_target", association)
-              association_proxy.__send__(:set_inverse_instance, association, record)
-            end
-
-          # A JoinPart represents a part of a JoinDependency. It is an abstract class, inherited
-          # by JoinBase and JoinAssociation. A JoinBase represents the Active Record which
-          # everything else is being joined onto. A JoinAssociation represents an association which
-          # is joining to the base. A JoinAssociation may result in more than one actual join
-          # 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:
-            # 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 :active_record
-
-            delegate :table_name, :column_names, :primary_key, :reflections, :sanitize_sql, :arel_engine, :to => :active_record
-
-            def initialize(active_record)
-              @active_record = active_record
-              @cached_record = {}
-            end
-
-            def ==(other)
-              raise NotImplementedError
-            end
-
-            # An Arel::Table for the active_record
-            def table
-              raise NotImplementedError
-            end
-
-            # The prefix to be used when aliasing columns in the active_record's table
-            def aliased_prefix
-              raise NotImplementedError
-            end
-
-            # The alias for the active_record's table
-            def aliased_table_name
-              raise NotImplementedError
-            end
-
-            # The alias for the primary key of the active_record's table
-            def aliased_primary_key
-              "#{aliased_prefix}_r0"
-            end
-
-            # An array of [column_name, alias] pairs for the table
-            def column_names_with_alias
-              unless defined?(@column_names_with_alias)
-                @column_names_with_alias = []
-
-                ([primary_key] + (column_names - [primary_key])).each_with_index do |column_name, i|
-                  @column_names_with_alias << [column_name, "#{aliased_prefix}_r#{i}"]
-                end
-              end
-
-              @column_names_with_alias
-            end
-
-            def extract_record(row)
-              Hash[column_names_with_alias.map{|cn, an| [cn, row[an]]}]
-            end
-
-            def record_id(row)
-              row[aliased_primary_key]
-            end
-
-            def instantiate(row)
-              @cached_record[record_id(row)] ||= active_record.send(:instantiate, extract_record(row))
-            end
-          end
-
-          class JoinBase < JoinPart # :nodoc:
-            # Extra joins provided when the JoinDependency was created
-            attr_reader :table_joins
-
-            def initialize(active_record, joins = nil)
-              super(active_record)
-              @table_joins = joins
-            end
-
-            def ==(other)
-              other.class == self.class &&
-              other.active_record == active_record
-            end
-
-            def aliased_prefix
-              "t0"
-            end
-
-            def table
-              Arel::Table.new(table_name, :engine => arel_engine, :columns => active_record.columns)
-            end
-
-            def aliased_table_name
-              active_record.table_name
-            end
-          end
-
-          class JoinAssociation < JoinPart # :nodoc:
-            # The reflection of the association represented
-            attr_reader :reflection
-
-            # The JoinDependency object which this JoinAssociation exists within. This is mainly
-            # relevant for generating aliases which do not conflict with other joins which are
-            # part of the query.
-            attr_reader :join_dependency
-
-            # 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
-
-            # What type of join will be generated, either Arel::InnerJoin (default) or Arel::OuterJoin
-            attr_accessor :join_type
-
-            # These implement abstract methods from the superclass
-            attr_reader :aliased_prefix, :aliased_table_name
-
-            delegate :options, :through_reflection, :source_reflection, :to => :reflection
-            delegate :table, :table_name, :to => :parent, :prefix => true
-
-            def initialize(reflection, join_dependency, parent = nil)
-              reflection.check_validity!
-
-              if reflection.options[:polymorphic]
-                raise EagerLoadPolymorphicError.new(reflection)
-              end
-
-              super(reflection.klass)
-
-              @reflection      = reflection
-              @join_dependency = join_dependency
-              @parent          = parent
-              @join_type       = Arel::InnerJoin
-
-              # This must be done eagerly upon initialisation because the alias which is produced
-              # depends on the state of the join dependency, but we want it to work the same way
-              # every time.
-              allocate_aliases
-            end
-
-            def ==(other)
-              other.class == self.class &&
-              other.reflection == reflection &&
-              other.parent == parent
-            end
-
-            def find_parent_in(other_join_dependency)
-              other_join_dependency.join_parts.detect do |join_part|
-                self.parent == join_part
-              end
-            end
-
-            def join_to(relation)
-              send("join_#{reflection.macro}_to", relation)
-            end
-
-            def join_relation(joining_relation)
-              self.join_type = Arel::OuterJoin
-              joining_relation.joins(self)
-            end
-
-            def table
-              @table ||= Arel::Table.new(
-                table_name, :as => aliased_table_name,
-                :engine => arel_engine, :columns => active_record.columns
-              )
-            end
-
-            # More semantic name given we are talking about associations
-            alias_method :target_table, :table
-
-            protected
-
-              def aliased_table_name_for(name, suffix = nil)
-                if @join_dependency.table_aliases[name].zero?
-                  @join_dependency.table_aliases[name] = @join_dependency.count_aliases_from_table_joins(name)
-                end
-
-                if !@join_dependency.table_aliases[name].zero? # We need an alias
-                  name = active_record.connection.table_alias_for "#{pluralize(reflection.name)}_#{parent_table_name}#{suffix}"
-                  @join_dependency.table_aliases[name] += 1
-                  if @join_dependency.table_aliases[name] == 1 # First time we've seen this name
-                    # Also need to count the aliases from the table_aliases to avoid incorrect count
-                    @join_dependency.table_aliases[name] += @join_dependency.count_aliases_from_table_joins(name)
-                  end
-                  table_index = @join_dependency.table_aliases[name]
-                  name = name[0..active_record.connection.table_alias_length-3] + "_#{table_index}" if table_index > 1
-                else
-                  @join_dependency.table_aliases[name] += 1
-                end
-
-                name
-              end
-
-              def pluralize(table_name)
-                ActiveRecord::Base.pluralize_table_names ? table_name.to_s.pluralize : table_name
-              end
-
-              def interpolate_sql(sql)
-                instance_eval("%@#{sql.gsub('@', '\@')}@", __FILE__, __LINE__)
-              end
-
-            private
-
-            def allocate_aliases
-              @aliased_prefix     = "t#{ join_dependency.join_parts.size }"
-              @aliased_table_name = aliased_table_name_for(table_name)
-
-              if reflection.macro == :has_and_belongs_to_many
-                @aliased_join_table_name = aliased_table_name_for(reflection.options[:join_table], "_join")
-              elsif [:has_many, :has_one].include?(reflection.macro) && reflection.options[:through]
-                @aliased_join_table_name = aliased_table_name_for(reflection.through_reflection.klass.table_name, "_join")
-              end
-            end
-
-            def process_conditions(conditions, table_name)
-              Arel.sql(interpolate_sql(sanitize_sql(conditions, table_name)))
-            end
-
-            def join_target_table(relation, *conditions)
-              relation = relation.join(target_table, join_type)
-
-              # If the target table is an STI model then we must be sure to only include records of
-              # its type and its sub-types.
-              unless active_record.descends_from_active_record?
-                sti_column = target_table[active_record.inheritance_column]
-
-                sti_condition = sti_column.eq(active_record.sti_name)
-                active_record.descendants.each do |subclass|
-                  sti_condition = sti_condition.or(sti_column.eq(subclass.sti_name))
-                end
-
-                conditions << sti_condition
-              end
-
-              # If the reflection has conditions, add them
-              if options[:conditions]
-                conditions << process_conditions(options[:conditions], aliased_table_name)
-              end
-
-              relation = relation.on(*conditions)
-            end
-
-            def join_has_and_belongs_to_many_to(relation)
-              join_table = Arel::Table.new(
-                options[:join_table], :engine => arel_engine,
-                :as => @aliased_join_table_name
-              )
-
-              fk       = options[:foreign_key]             || reflection.active_record.to_s.foreign_key
-              klass_fk = options[:association_foreign_key] || reflection.klass.to_s.foreign_key
-
-              relation = relation.join(join_table, join_type)
-              relation = relation.on(
-                join_table[fk].
-                  eq(parent_table[reflection.active_record.primary_key])
-              )
-
-              join_target_table(
-                relation,
-                target_table[reflection.klass.primary_key].
-                  eq(join_table[klass_fk])
-              )
-            end
-
-            def join_has_many_to(relation)
-              if reflection.options[:through]
-                join_has_many_through_to(relation)
-              elsif reflection.options[:as]
-                join_has_many_polymorphic_to(relation)
-              else
-                foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key
-                primary_key = options[:primary_key] || parent.primary_key
-
-                join_target_table(
-                  relation,
-                  target_table[foreign_key].
-                    eq(parent_table[primary_key])
-                )
-              end
-            end
-            alias :join_has_one_to :join_has_many_to
-
-            def join_has_many_through_to(relation)
-              join_table = Arel::Table.new(
-                through_reflection.klass.table_name, :engine => arel_engine,
-                :as => @aliased_join_table_name
-              )
-
-              jt_conditions = []
-              jt_foreign_key = first_key = second_key = nil
-
-              if through_reflection.options[:as] # has_many :through against a polymorphic join
-                as_key         = through_reflection.options[:as].to_s
-                jt_foreign_key = as_key + '_id'
-
-                jt_conditions <<
-                  join_table[as_key + '_type'].
-                    eq(parent.active_record.base_class.name)
-              else
-                jt_foreign_key = through_reflection.primary_key_name
-              end
-
-              case source_reflection.macro
-              when :has_many
-                second_key = options[:foreign_key] || primary_key
-
-                if source_reflection.options[:as]
-                  first_key = "#{source_reflection.options[:as]}_id"
-                else
-                  first_key = through_reflection.klass.base_class.to_s.foreign_key
-                end
-
-                unless through_reflection.klass.descends_from_active_record?
-                  jt_conditions <<
-                    join_table[through_reflection.active_record.inheritance_column].
-                      eq(through_reflection.klass.sti_name)
-                end
-              when :belongs_to
-                first_key = primary_key
-
-                if reflection.options[:source_type]
-                  second_key = source_reflection.association_foreign_key
-
-                  jt_conditions <<
-                    join_table[reflection.source_reflection.options[:foreign_type]].
-                      eq(reflection.options[:source_type])
-                else
-                  second_key = source_reflection.primary_key_name
-                end
-              end
-
-              jt_conditions <<
-                parent_table[parent.primary_key].
-                  eq(join_table[jt_foreign_key])
-
-              if through_reflection.options[:conditions]
-                jt_conditions << process_conditions(through_reflection.options[:conditions], aliased_table_name)
-              end
-
-              relation = relation.join(join_table, join_type).on(*jt_conditions)
-
-              join_target_table(
-                relation,
-                target_table[first_key].eq(join_table[second_key])
-              )
-            end
-
-            def join_has_many_polymorphic_to(relation)
-              join_target_table(
-                relation,
-                target_table["#{reflection.options[:as]}_id"].
-                  eq(parent_table[parent.primary_key]),
-                target_table["#{reflection.options[:as]}_type"].
-                  eq(parent.active_record.base_class.name)
-              )
-            end
-
-            def join_belongs_to_to(relation)
-              foreign_key = options[:foreign_key] || reflection.primary_key_name
-              primary_key = options[:primary_key] || reflection.klass.primary_key
-
-              join_target_table(
-                relation,
-                target_table[primary_key].eq(parent_table[foreign_key])
-              )
-            end
-          end
-        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/associations/class_methods/join_dependency.rb b/activerecord/lib/active_record/associations/class_methods/join_dependency.rb
new file mode 100644
index 0000000000..79fdb2d4cb
--- /dev/null
+++ b/activerecord/lib/active_record/associations/class_methods/join_dependency.rb
@@ -0,0 +1,216 @@
+require 'active_record/associations/class_methods/join_dependency/join_part'
+require 'active_record/associations/class_methods/join_dependency/join_base'
+require 'active_record/associations/class_methods/join_dependency/join_association'
+
+module ActiveRecord
+  module Associations
+    module ClassMethods
+      class JoinDependency # :nodoc:
+        attr_reader :join_parts, :reflections, :table_aliases
+
+        def initialize(base, associations, joins)
+          @join_parts            = [JoinBase.new(base, joins)]
+          @associations          = {}
+          @reflections           = []
+          @table_aliases         = Hash.new(0)
+          @table_aliases[base.table_name] = 1
+          build(associations)
+        end
+
+        def graft(*associations)
+          associations.each do |association|
+            join_associations.detect {|a| association == a} ||
+              build(association.reflection.name, association.find_parent_in(self) || join_base, association.join_type)
+          end
+          self
+        end
+
+        def join_associations
+          join_parts.last(join_parts.length - 1)
+        end
+
+        def join_base
+          join_parts.first
+        end
+
+        def count_aliases_from_table_joins(name)
+          # quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
+          quoted_name = join_base.active_record.connection.quote_table_name(name.downcase).downcase
+          join_sql = join_base.table_joins.to_s.downcase
+          join_sql.blank? ? 0 :
+            # Table names
+            join_sql.scan(/join(?:\s+\w+)?\s+#{quoted_name}\son/).size +
+            # Table aliases
+            join_sql.scan(/join(?:\s+\w+)?\s+\S+\s+#{quoted_name}\son/).size
+        end
+
+        def instantiate(rows)
+          primary_key = join_base.aliased_primary_key
+          parents = {}
+
+          records = rows.map { |model|
+            primary_id = model[primary_key]
+            parent = parents[primary_id] ||= join_base.instantiate(model)
+            construct(parent, @associations, join_associations.dup, model)
+            parent
+          }.uniq
+
+          remove_duplicate_results!(join_base.active_record, records, @associations)
+          records
+        end
+
+        def remove_duplicate_results!(base, records, associations)
+          case associations
+          when Symbol, String
+            reflection = base.reflections[associations]
+            remove_uniq_by_reflection(reflection, records)
+          when Array
+            associations.each do |association|
+              remove_duplicate_results!(base, records, association)
+            end
+          when Hash
+            associations.keys.each do |name|
+              reflection = base.reflections[name]
+              remove_uniq_by_reflection(reflection, records)
+
+              parent_records = []
+              records.each do |record|
+                if descendant = record.send(reflection.name)
+                  if reflection.collection?
+                    parent_records.concat descendant.target.uniq
+                  else
+                    parent_records << descendant
+                  end
+                end
+              end
+
+              remove_duplicate_results!(reflection.klass, parent_records, associations[name]) unless parent_records.empty?
+            end
+          end
+        end
+
+        protected
+
+        def cache_joined_association(association)
+          associations = []
+          parent = association.parent
+          while parent != join_base
+            associations.unshift(parent.reflection.name)
+            parent = parent.parent
+          end
+          ref = @associations
+          associations.each do |key|
+            ref = ref[key]
+          end
+          ref[association.reflection.name] ||= {}
+        end
+
+        def build(associations, parent = nil, join_type = Arel::InnerJoin)
+          parent ||= join_parts.last
+          case associations
+          when Symbol, String
+            reflection = parent.reflections[associations.to_s.intern] or
+            raise ConfigurationError, "Association named '#{ associations }' was not found; perhaps you misspelled it?"
+            unless join_association = find_join_association(reflection, parent)
+              @reflections << reflection
+              join_association = build_join_association(reflection, parent)
+              join_association.join_type = join_type
+              @join_parts << join_association
+              cache_joined_association(join_association)
+            end
+            join_association
+          when Array
+            associations.each do |association|
+              build(association, parent, join_type)
+            end
+          when Hash
+            associations.keys.sort{|a,b|a.to_s<=>b.to_s}.each do |name|
+              join_association = build(name, parent, join_type)
+              build(associations[name], join_association, join_type)
+            end
+          else
+            raise ConfigurationError, associations.inspect
+          end
+        end
+
+        def find_join_association(name_or_reflection, parent)
+          if String === name_or_reflection
+            name_or_reflection = name_or_reflection.to_sym
+          end
+
+          join_associations.detect { |j|
+            j.reflection == name_or_reflection && j.parent == parent
+          }
+        end
+
+        def remove_uniq_by_reflection(reflection, records)
+          if reflection && reflection.collection?
+            records.each { |record| record.send(reflection.name).target.uniq! }
+          end
+        end
+
+        def build_join_association(reflection, parent)
+          JoinAssociation.new(reflection, self, parent)
+        end
+
+        def construct(parent, associations, join_parts, row)
+          case associations
+          when Symbol, String
+            name = associations.to_s
+
+            join_part = join_parts.detect { |j|
+              j.reflection.name.to_s == name &&
+                j.parent_table_name    == parent.class.table_name }
+
+              raise(ConfigurationError, "No such association") unless join_part
+
+              join_parts.delete(join_part)
+              construct_association(parent, join_part, row)
+          when Array
+            associations.each do |association|
+              construct(parent, association, join_parts, row)
+            end
+          when Hash
+            associations.sort_by { |k,_| k.to_s }.each do |name, assoc|
+              association = construct(parent, name, join_parts, row)
+              construct(association, assoc, join_parts, row) if association
+            end
+          else
+            raise ConfigurationError, associations.inspect
+          end
+        end
+
+        def construct_association(record, join_part, row)
+          return if record.id.to_s != join_part.parent.record_id(row).to_s
+
+          macro = join_part.reflection.macro
+          if macro == :has_one
+            return if record.instance_variable_defined?("@#{join_part.reflection.name}")
+            association = join_part.instantiate(row) unless row[join_part.aliased_primary_key].nil?
+            set_target_and_inverse(join_part, association, record)
+          else
+            return if row[join_part.aliased_primary_key].nil?
+            association = join_part.instantiate(row)
+            case macro
+            when :has_many, :has_and_belongs_to_many
+              collection = record.send(join_part.reflection.name)
+              collection.loaded
+              collection.target.push(association)
+              collection.__send__(:set_inverse_instance, association, record)
+            when :belongs_to
+              set_target_and_inverse(join_part, association, record)
+            else
+              raise ConfigurationError, "unknown macro: #{join_part.reflection.macro}"
+            end
+          end
+          association
+        end
+
+        def set_target_and_inverse(join_part, association, record)
+          association_proxy = record.send("set_#{join_part.reflection.name}_target", association)
+          association_proxy.__send__(:set_inverse_instance, association, record)
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/associations/class_methods/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_association.rb
new file mode 100644
index 0000000000..5e5c01c77a
--- /dev/null
+++ b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_association.rb
@@ -0,0 +1,278 @@
+module ActiveRecord
+  module Associations
+    module ClassMethods
+      class JoinDependency # :nodoc:
+        class JoinAssociation < JoinPart # :nodoc:
+          # The reflection of the association represented
+          attr_reader :reflection
+
+          # The JoinDependency object which this JoinAssociation exists within. This is mainly
+          # relevant for generating aliases which do not conflict with other joins which are
+          # part of the query.
+          attr_reader :join_dependency
+
+          # 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
+
+          # What type of join will be generated, either Arel::InnerJoin (default) or Arel::OuterJoin
+          attr_accessor :join_type
+
+          # These implement abstract methods from the superclass
+          attr_reader :aliased_prefix, :aliased_table_name
+
+          delegate :options, :through_reflection, :source_reflection, :to => :reflection
+          delegate :table, :table_name, :to => :parent, :prefix => true
+
+          def initialize(reflection, join_dependency, parent = nil)
+            reflection.check_validity!
+
+            if reflection.options[:polymorphic]
+              raise EagerLoadPolymorphicError.new(reflection)
+            end
+
+            super(reflection.klass)
+
+            @reflection      = reflection
+            @join_dependency = join_dependency
+            @parent          = parent
+            @join_type       = Arel::InnerJoin
+
+            # This must be done eagerly upon initialisation because the alias which is produced
+            # depends on the state of the join dependency, but we want it to work the same way
+            # every time.
+            allocate_aliases
+          end
+
+          def ==(other)
+            other.class == self.class &&
+              other.reflection == reflection &&
+              other.parent == parent
+          end
+
+          def find_parent_in(other_join_dependency)
+            other_join_dependency.join_parts.detect do |join_part|
+              self.parent == join_part
+            end
+          end
+
+          def join_to(relation)
+            send("join_#{reflection.macro}_to", relation)
+          end
+
+          def join_relation(joining_relation)
+            self.join_type = Arel::OuterJoin
+            joining_relation.joins(self)
+          end
+
+          def table
+            @table ||= Arel::Table.new(
+              table_name, :as => aliased_table_name,
+              :engine => arel_engine, :columns => active_record.columns
+            )
+          end
+
+          # More semantic name given we are talking about associations
+          alias_method :target_table, :table
+
+          protected
+
+          def aliased_table_name_for(name, suffix = nil)
+            if @join_dependency.table_aliases[name].zero?
+              @join_dependency.table_aliases[name] = @join_dependency.count_aliases_from_table_joins(name)
+            end
+
+            if !@join_dependency.table_aliases[name].zero? # We need an alias
+              name = active_record.connection.table_alias_for "#{pluralize(reflection.name)}_#{parent_table_name}#{suffix}"
+              @join_dependency.table_aliases[name] += 1
+              if @join_dependency.table_aliases[name] == 1 # First time we've seen this name
+                # Also need to count the aliases from the table_aliases to avoid incorrect count
+                @join_dependency.table_aliases[name] += @join_dependency.count_aliases_from_table_joins(name)
+              end
+              table_index = @join_dependency.table_aliases[name]
+              name = name[0..active_record.connection.table_alias_length-3] + "_#{table_index}" if table_index > 1
+            else
+              @join_dependency.table_aliases[name] += 1
+            end
+
+            name
+          end
+
+          def pluralize(table_name)
+            ActiveRecord::Base.pluralize_table_names ? table_name.to_s.pluralize : table_name
+          end
+
+          def interpolate_sql(sql)
+            instance_eval("%@#{sql.gsub('@', '\@')}@", __FILE__, __LINE__)
+          end
+
+          private
+
+          def allocate_aliases
+            @aliased_prefix     = "t#{ join_dependency.join_parts.size }"
+            @aliased_table_name = aliased_table_name_for(table_name)
+
+            if reflection.macro == :has_and_belongs_to_many
+              @aliased_join_table_name = aliased_table_name_for(reflection.options[:join_table], "_join")
+            elsif [:has_many, :has_one].include?(reflection.macro) && reflection.options[:through]
+              @aliased_join_table_name = aliased_table_name_for(reflection.through_reflection.klass.table_name, "_join")
+            end
+          end
+
+          def process_conditions(conditions, table_name)
+            Arel.sql(interpolate_sql(sanitize_sql(conditions, table_name)))
+          end
+
+          def join_target_table(relation, *conditions)
+            relation = relation.join(target_table, join_type)
+
+            # If the target table is an STI model then we must be sure to only include records of
+            # its type and its sub-types.
+            unless active_record.descends_from_active_record?
+              sti_column = target_table[active_record.inheritance_column]
+
+              sti_condition = sti_column.eq(active_record.sti_name)
+              active_record.descendants.each do |subclass|
+                sti_condition = sti_condition.or(sti_column.eq(subclass.sti_name))
+              end
+
+              conditions << sti_condition
+            end
+
+            # If the reflection has conditions, add them
+            if options[:conditions]
+              conditions << process_conditions(options[:conditions], aliased_table_name)
+            end
+
+            relation = relation.on(*conditions)
+          end
+
+          def join_has_and_belongs_to_many_to(relation)
+            join_table = Arel::Table.new(
+              options[:join_table], :engine => arel_engine,
+              :as => @aliased_join_table_name
+            )
+
+            fk       = options[:foreign_key]             || reflection.active_record.to_s.foreign_key
+            klass_fk = options[:association_foreign_key] || reflection.klass.to_s.foreign_key
+
+            relation = relation.join(join_table, join_type)
+            relation = relation.on(
+              join_table[fk].
+              eq(parent_table[reflection.active_record.primary_key])
+            )
+
+            join_target_table(
+              relation,
+              target_table[reflection.klass.primary_key].
+              eq(join_table[klass_fk])
+            )
+          end
+
+          def join_has_many_to(relation)
+            if reflection.options[:through]
+              join_has_many_through_to(relation)
+            elsif reflection.options[:as]
+              join_has_many_polymorphic_to(relation)
+            else
+              foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key
+              primary_key = options[:primary_key] || parent.primary_key
+
+              join_target_table(
+                relation,
+                target_table[foreign_key].
+                eq(parent_table[primary_key])
+              )
+            end
+          end
+          alias :join_has_one_to :join_has_many_to
+
+          def join_has_many_through_to(relation)
+            join_table = Arel::Table.new(
+              through_reflection.klass.table_name, :engine => arel_engine,
+              :as => @aliased_join_table_name
+            )
+
+            jt_conditions = []
+            jt_foreign_key = first_key = second_key = nil
+
+            if through_reflection.options[:as] # has_many :through against a polymorphic join
+              as_key         = through_reflection.options[:as].to_s
+              jt_foreign_key = as_key + '_id'
+
+              jt_conditions <<
+              join_table[as_key + '_type'].
+                eq(parent.active_record.base_class.name)
+            else
+              jt_foreign_key = through_reflection.primary_key_name
+            end
+
+            case source_reflection.macro
+            when :has_many
+              second_key = options[:foreign_key] || primary_key
+
+              if source_reflection.options[:as]
+                first_key = "#{source_reflection.options[:as]}_id"
+              else
+                first_key = through_reflection.klass.base_class.to_s.foreign_key
+              end
+
+              unless through_reflection.klass.descends_from_active_record?
+                jt_conditions <<
+                join_table[through_reflection.active_record.inheritance_column].
+                  eq(through_reflection.klass.sti_name)
+              end
+            when :belongs_to
+              first_key = primary_key
+
+              if reflection.options[:source_type]
+                second_key = source_reflection.association_foreign_key
+
+                jt_conditions <<
+                join_table[reflection.source_reflection.options[:foreign_type]].
+                  eq(reflection.options[:source_type])
+              else
+                second_key = source_reflection.primary_key_name
+              end
+            end
+
+            jt_conditions <<
+            parent_table[parent.primary_key].
+              eq(join_table[jt_foreign_key])
+
+            if through_reflection.options[:conditions]
+              jt_conditions << process_conditions(through_reflection.options[:conditions], aliased_table_name)
+            end
+
+            relation = relation.join(join_table, join_type).on(*jt_conditions)
+
+            join_target_table(
+              relation,
+              target_table[first_key].eq(join_table[second_key])
+            )
+          end
+
+          def join_has_many_polymorphic_to(relation)
+            join_target_table(
+              relation,
+              target_table["#{reflection.options[:as]}_id"].
+              eq(parent_table[parent.primary_key]),
+              target_table["#{reflection.options[:as]}_type"].
+              eq(parent.active_record.base_class.name)
+            )
+          end
+
+          def join_belongs_to_to(relation)
+            foreign_key = options[:foreign_key] || reflection.primary_key_name
+            primary_key = options[:primary_key] || reflection.klass.primary_key
+
+            join_target_table(
+              relation,
+              target_table[primary_key].eq(parent_table[foreign_key])
+            )
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/associations/class_methods/join_dependency/join_base.rb b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_base.rb
new file mode 100644
index 0000000000..ed05003f66
--- /dev/null
+++ b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_base.rb
@@ -0,0 +1,34 @@
+module ActiveRecord
+  module Associations
+    module ClassMethods
+      class JoinDependency # :nodoc:
+        class JoinBase < JoinPart # :nodoc:
+          # Extra joins provided when the JoinDependency was created
+          attr_reader :table_joins
+
+          def initialize(active_record, joins = nil)
+            super(active_record)
+            @table_joins = joins
+          end
+
+          def ==(other)
+            other.class == self.class &&
+              other.active_record == active_record
+          end
+
+          def aliased_prefix
+            "t0"
+          end
+
+          def table
+            Arel::Table.new(table_name, :engine => arel_engine, :columns => active_record.columns)
+          end
+
+          def aliased_table_name
+            active_record.table_name
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/associations/class_methods/join_dependency/join_part.rb b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_part.rb
new file mode 100644
index 0000000000..64d751344d
--- /dev/null
+++ b/activerecord/lib/active_record/associations/class_methods/join_dependency/join_part.rb
@@ -0,0 +1,76 @@
+module ActiveRecord
+  module Associations
+    module ClassMethods
+      class JoinDependency # :nodoc:
+        # A JoinPart represents a part of a JoinDependency. It is an abstract class, inherited
+        # by JoinBase and JoinAssociation. A JoinBase represents the Active Record which
+        # everything else is being joined onto. A JoinAssociation represents an association which
+        # is joining to the base. A JoinAssociation may result in more than one actual join
+        # 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:
+          # 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 :active_record
+
+          delegate :table_name, :column_names, :primary_key, :reflections, :sanitize_sql, :arel_engine, :to => :active_record
+
+          def initialize(active_record)
+            @active_record = active_record
+            @cached_record = {}
+          end
+
+          def ==(other)
+            raise NotImplementedError
+          end
+
+          # An Arel::Table for the active_record
+          def table
+            raise NotImplementedError
+          end
+
+          # The prefix to be used when aliasing columns in the active_record's table
+          def aliased_prefix
+            raise NotImplementedError
+          end
+
+          # The alias for the active_record's table
+          def aliased_table_name
+            raise NotImplementedError
+          end
+
+          # The alias for the primary key of the active_record's table
+          def aliased_primary_key
+            "#{aliased_prefix}_r0"
+          end
+
+          # An array of [column_name, alias] pairs for the table
+          def column_names_with_alias
+            unless defined?(@column_names_with_alias)
+              @column_names_with_alias = []
+
+              ([primary_key] + (column_names - [primary_key])).each_with_index do |column_name, i|
+                @column_names_with_alias << [column_name, "#{aliased_prefix}_r#{i}"]
+              end
+            end
+
+            @column_names_with_alias
+          end
+
+          def extract_record(row)
+            Hash[column_names_with_alias.map{|cn, an| [cn, row[an]]}]
+          end
+
+          def record_id(row)
+            row[aliased_primary_key]
+          end
+
+          def instantiate(row)
+            @cached_record[record_id(row)] ||= active_record.send(:instantiate, extract_record(row))
+          end
+        end
+      end
+    end
+  end
+end