Eager Loading support added for has_many :through => :has_many associations...

Eager Loading support added for has_many :through => :has_many associations (see below).  [Rick Olson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3967 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/associations.rb

@@ -1244,7 +1244,7 @@ def instantiate(row)
 
           class JoinAssociation < JoinBase
             attr_reader :reflection, :parent, :aliased_table_name, :aliased_prefix, :aliased_join_table_name, :parent_table_name
-            delegate    :options, :klass, :to => :reflection
+            delegate    :options, :klass, :through_reflection, :source_reflection, :to => :reflection
 
             def initialize(reflection, join_dependency, parent = nil)
               reflection.check_validity!
@@ -1291,7 +1291,6 @@ def association_join
                 when :has_many, :has_one
                   case
                     when reflection.macro == :has_many && reflection.options[:through]
-                      through_reflection = parent.active_record.reflect_on_association(reflection.options[:through])
                       through_conditions = through_reflection.options[:conditions] ? "AND #{interpolate_sql(sanitize_sql(through_reflection.options[:conditions]))}" : ''
                       if through_reflection.options[:as] # has_many :through against a polymorphic join
                         polymorphic_foreign_key  = through_reflection.options[:as].to_s + '_id'
@@ -1305,16 +1304,26 @@ def association_join
                         " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [table_name_and_alias,
                           aliased_table_name, primary_key, aliased_join_table_name, options[:foreign_key] || reflection.klass.to_s.classify.foreign_key
                         ]
-                      else # has_many :through against a normal join
+                      elsif source_reflection.macro == :belongs_to # has_many :through against a belongs_to
                         " LEFT OUTER JOIN %s ON %s.%s = %s.%s "  % [
                           table_alias_for(through_reflection.klass.table_name, aliased_join_table_name), aliased_join_table_name,
-                          through_reflection.options[:foreign_key] || through_reflection.active_record.to_s.classify.foreign_key,
+                          through_reflection.primary_key_name,
                           parent.aliased_table_name, parent.primary_key] +
                         " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                           table_name_and_alias,
                           aliased_table_name, primary_key, 
                           aliased_join_table_name, options[:foreign_key] || klass.to_s.classify.foreign_key
                         ]
+                      elsif source_reflection.macro == :has_many # has_many :through against a has_many
+                        " LEFT OUTER JOIN %s ON %s.%s = %s.%s "  % [
+                          table_alias_for(through_reflection.klass.table_name, aliased_join_table_name), aliased_join_table_name,
+                          through_reflection.primary_key_name,
+                          parent.aliased_table_name, parent.primary_key] +
+                        " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
+                          table_name_and_alias,
+                          aliased_table_name, through_reflection.klass.to_s.classify.foreign_key, 
+                          aliased_join_table_name, options[:foreign_key] || primary_key
+                        ]
                       end
                       
                     when reflection.macro == :has_many && reflection.options[:as]
@@ -1325,6 +1334,7 @@ def association_join
                         aliased_table_name, "#{reflection.options[:as]}_type",
                         klass.quote(parent.active_record.base_class.name)
                       ]
+                      
                     else
                       " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                         table_name_and_alias,

activerecord/test/associations_join_model_test.rb

@@ -231,11 +231,11 @@ def test_has_many_polymorphic
   end
 
   def test_has_many_through_has_many_find_all
-    assert_equal comments(:greetings), authors(:david).comments.find(:all).first
+    assert_equal comments(:greetings), authors(:david).comments.find(:all, :order => 'comments.id').first
   end
 
   def test_has_many_through_has_many_find_first
-    assert_equal comments(:greetings), authors(:david).comments.find(:first)
+    assert_equal comments(:greetings), authors(:david).comments.find(:first, :order => 'comments.id')
   end
 
   def test_has_many_through_has_many_find_conditions
@@ -246,6 +246,14 @@ def test_has_many_through_has_many_find_by_id
     assert_equal comments(:more_greetings), authors(:david).comments.find(2)
   end
 
+  def test_eager_load_has_many_through_has_many
+    author = Author.find :first, :conditions => ['name = ?', 'David'], :include => :comments, :order => 'comments.id'
+    SpecialComment.new; VerySpecialComment.new
+    assert_no_queries do
+      assert_equal [1,2,3,5,6,7,8,9,10], author.comments.collect(&:id)
+    end
+  end
+
   private
     # create dynamic Post models to allow different dependency options
     def find_post_with_dependency(post_id, association, association_name, dependency)