Properly support conditions on any of the reflections involved in a nested through association

activerecord/lib/active_record/associations.rb

@@ -2164,8 +2164,10 @@ def join_to(relation)
               chain = through_reflection_chain.reverse
               
               foreign_table = parent_table
+              index = 0
               
-              chain.zip(@tables).each do |reflection, table|
+              chain.each do |reflection|
+                table = @tables[index]
                 conditions = []
                 
                 if reflection.source_reflection.nil?
@@ -2234,13 +2236,14 @@ def join_to(relation)
                 
                 conditions << table[key].eq(foreign_table[foreign_key])
                 
-                conditions << reflection_conditions(reflection, table)
+                conditions << reflection_conditions(index, table)
                 conditions << sti_conditions(reflection, table)
                 
-                relation = relation.join(table, join_type).on(*conditions.compact)
+                relation = relation.join(table, join_type).on(*conditions.flatten.compact)
                 
                 # The current table in this iteration becomes the foreign table in the next
                 foreign_table = table
+                index += 1
               end
               
               relation
@@ -2325,10 +2328,10 @@ def setup_tables
               @tables
             end
             
-            def reflection_conditions(reflection, table)
+            def reflection_conditions(index, table)
-              if reflection.options[:conditions]
+              @reflection.through_conditions.reverse[index].map do |condition|
                 Arel.sql(interpolate_sql(sanitize_sql(
-                  reflection.options[:conditions],
+                  condition,
                   table.table_alias || table.name
                 )))
               end

activerecord/lib/active_record/associations/through_association_scope.rb

@@ -24,7 +24,6 @@ def construct_create_scope
       end
 
       # Build SQL conditions from attributes, qualified by table name.
-      # TODO: Conditions on joins
       def construct_conditions
         reflection = @reflection.through_reflection_chain.last
         
@@ -34,11 +33,12 @@ def construct_conditions
           table_alias = table_aliases[reflection]
         end
         
-        conditions = construct_quoted_owner_attributes(reflection).map do |attr, value|
+        parts = construct_quoted_owner_attributes(reflection).map do |attr, value|
           "#{table_alias}.#{attr} = #{value}"
         end
-        conditions << sql_conditions if sql_conditions
+        parts += reflection_conditions(0)
-        "(" + conditions.join(') AND (') + ")"
+        
+        "(" + parts.join(') AND (') + ")"
       end
 
       # Associate attributes pointing to owner, quoted.
@@ -55,23 +55,21 @@ def construct_quoted_owner_attributes(reflection)
         end
       end
 
-      def construct_from
-        @reflection.table_name
-      end
-
       def construct_select(custom_select = nil)
         distinct = "DISTINCT " if @reflection.options[:uniq]
         selected = custom_select || @reflection.options[:select] || "#{distinct}#{@reflection.quoted_table_name}.*"
       end
       
       def construct_joins(custom_joins = nil)
-        # p @reflection.through_reflection_chain
+        # TODO: Remove this at the end
+        #p @reflection.through_reflection_chain
+        #p @reflection.through_conditions
         
         "#{construct_through_joins} #{@reflection.options[:joins]} #{custom_joins}"
       end
 
       def construct_through_joins
-        joins = []
+        joins, right_index = [], 1
         
         # Iterate over each pair in the through reflection chain, joining them together
         @reflection.through_reflection_chain.each_cons(2) do |left, right|
@@ -86,20 +84,23 @@ def construct_through_joins
                 joins << inner_join_sql(
                   right_table_and_alias,
                   table_aliases[left],  left.klass.primary_key,
-                  table_aliases[right], left.primary_key_name
+                  table_aliases[right], left.primary_key_name,
+                  reflection_conditions(right_index)
                 )
               when :has_many, :has_one
                 joins << inner_join_sql(
                   right_table_and_alias,
                   table_aliases[left],  left.primary_key_name,
                   table_aliases[right], right.klass.primary_key,
-                  polymorphic_conditions(left, left)
+                  polymorphic_conditions(left, left),
+                  reflection_conditions(right_index)
                 )
               when :has_and_belongs_to_many
                 joins << inner_join_sql(
                   right_table_and_alias,
                   table_aliases[left].first, left.primary_key_name,
-                  table_aliases[right],      right.klass.primary_key
+                  table_aliases[right],      right.klass.primary_key,
+                  reflection_conditions(right_index)
                 )
             end
           else
@@ -109,7 +110,8 @@ def construct_through_joins
                   right_table_and_alias,
                   table_aliases[left],  left.klass.primary_key,
                   table_aliases[right], left.source_reflection.primary_key_name,
-                  source_type_conditions(left)
+                  source_type_conditions(left),
+                  reflection_conditions(right_index)
                 )
               when :has_many, :has_one
                 if right.macro == :has_and_belongs_to_many
@@ -123,7 +125,8 @@ def construct_through_joins
                   right_table_and_alias,
                   table_aliases[left], left.source_reflection.primary_key_name,
                   right_table,         right.klass.primary_key,
-                  polymorphic_conditions(left, left.source_reflection)
+                  polymorphic_conditions(left, left.source_reflection),
+                  reflection_conditions(right_index)
                 )
                 
                 if right.macro == :has_and_belongs_to_many
@@ -151,10 +154,13 @@ def construct_through_joins
                 joins << inner_join_sql(
                   right_table_and_alias,
                   join_table,           left.source_reflection.primary_key_name,
-                  table_aliases[right], right.klass.primary_key
+                  table_aliases[right], right.klass.primary_key,
+                  reflection_conditions(right_index)
                 )
             end
           end
+          
+          right_index += 1
         end
         
         joins.join(" ")
@@ -206,18 +212,45 @@ def table_name_and_alias(table_name, table_alias)
         "#{table_name} #{table_alias if table_alias != table_name}".strip
       end
       
-      def inner_join_sql(table, on_left_table, on_left_key, on_right_table, on_right_key, conds = nil)
+      def inner_join_sql(table, on_left_table, on_left_key, on_right_table, on_right_key, *conditions)
-        "INNER JOIN %s ON %s.%s = %s.%s %s" % [
+        conditions << "#{on_left_table}.#{on_left_key} = #{on_right_table}.#{on_right_key}"
-          table,
+        conditions = conditions.flatten.compact
-          on_left_table,  on_left_key,
+        conditions = conditions.map { |sql| "(#{sql})" } * ' AND '
-          on_right_table, on_right_key,
+        
-          conds
+        "INNER JOIN #{table} ON #{conditions}"
-        ]
+      end
+      
+      def reflection_conditions(index)
+        reflection            = @reflection.through_reflection_chain[index]
+        reflection_conditions = @reflection.through_conditions[index]
+        
+        conditions = []
+        
+        if reflection.options[:as].nil? && # reflection.klass is a Module if :as is used
+           reflection.klass.finder_needs_type_condition?
+          conditions << reflection.klass.send(:type_condition).to_sql
+        end
+        
+        reflection_conditions.each do |condition|
+          sanitized_condition    = reflection.klass.send(:sanitize_sql, condition)
+          interpolated_condition = interpolate_sql(sanitized_condition)
+          
+          if condition.is_a?(Hash)
+            interpolated_condition.gsub!(
+              @reflection.quoted_table_name,
+              reflection.quoted_table_name
+            )
+          end
+          
+          conditions << interpolated_condition
+        end
+        
+        conditions
       end
       
       def polymorphic_conditions(reflection, polymorphic_reflection)
         if polymorphic_reflection.options[:as]
-          "AND %s.%s = %s" % [
+          "%s.%s = %s" % [
             table_aliases[reflection], "#{polymorphic_reflection.options[:as]}_type",
             @owner.class.quote_value(polymorphic_reflection.active_record.base_class.name)
           ]
@@ -226,7 +259,7 @@ def polymorphic_conditions(reflection, polymorphic_reflection)
       
       def source_type_conditions(reflection)
         if reflection.options[:source_type]
-          "AND %s.%s = %s" % [
+          "%s.%s = %s" % [
             table_aliases[reflection.through_reflection],
             reflection.source_reflection.options[:foreign_type].to_s,
             @owner.class.quote_value(reflection.options[:source_type])
@@ -245,6 +278,8 @@ def construct_owner_attributes(reflection)
       end
 
       # Construct attributes for :through pointing to owner and associate.
+      # This method is used when adding records to the association. Since this only makes sense for
+      # non-nested through associations, that's the only case we have to worry about here.
       def construct_join_attributes(associate)
         # TODO: revisit this to allow it for deletion, supposing dependent option is supported
         raise ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(@owner, @reflection) if [:has_one, :has_many].include?(@reflection.source_reflection.macro)
@@ -261,48 +296,6 @@ def construct_join_attributes(associate)
 
         join_attributes
       end
-
-      def conditions
-        @conditions = build_conditions unless defined?(@conditions)
-        @conditions
-      end
-
-      def build_conditions
-        association_conditions = @reflection.options[:conditions]
-        through_conditions = build_through_conditions
-        source_conditions = @reflection.source_reflection.options[:conditions]
-        uses_sti = !@reflection.through_reflection.klass.descends_from_active_record?
-
-        if association_conditions || through_conditions || source_conditions || uses_sti
-          all = []
-
-          [association_conditions, source_conditions].each do |conditions|
-            all << interpolate_sql(sanitize_sql(conditions)) if conditions
-          end
-
-          all << through_conditions  if through_conditions
-          all << build_sti_condition if uses_sti
-
-          all.map { |sql| "(#{sql})" } * ' AND '
-        end
-      end
-
-      def build_through_conditions
-        conditions = @reflection.through_reflection.options[:conditions]
-        if conditions.is_a?(Hash)
-          interpolate_sql(@reflection.through_reflection.klass.send(:sanitize_sql, conditions)).gsub(
-            @reflection.quoted_table_name,
-            @reflection.through_reflection.quoted_table_name)
-        elsif conditions
-          interpolate_sql(sanitize_sql(conditions))
-        end
-      end
-
-      def build_sti_condition
-        @reflection.through_reflection.klass.send(:type_condition).to_sql
-      end
-
-      alias_method :sql_conditions, :conditions
       
       def ensure_not_nested
         if @reflection.nested?

activerecord/lib/active_record/reflection.rb

@@ -253,6 +253,10 @@ def through_reflection
       def through_reflection_chain
         [self]
       end
+      
+      def through_conditions
+        [Array.wrap(options[:conditions])]
+      end
 
       def through_reflection_primary_key_name
       end
@@ -378,9 +382,9 @@ def through_reflection
       # TODO: Documentation
       def through_reflection_chain
         @through_reflection_chain ||= begin
-          if source_reflection.through_reflection
+          if source_reflection.source_reflection
-            # If the source reflection goes through another reflection, then the chain must start
+            # If the source reflection has its own source reflection, then the chain must start
-            # by getting us to the source reflection.
+            # by getting us to that source reflection.
             chain = source_reflection.through_reflection_chain
           else
             # If the source reflection does not go through another reflection, then we can get
@@ -396,6 +400,49 @@ def through_reflection_chain
         end
       end
       
+      # Consider the following example:
+      # 
+      #   class Person
+      #     has_many :articles
+      #     has_many :comment_tags, :through => :articles
+      #   end
+      # 
+      #   class Article
+      #     has_many :comments
+      #     has_many :comment_tags, :through => :comments, :source => :tags
+      #   end
+      # 
+      #   class Comment
+      #     has_many :tags
+      #   end
+      # 
+      # There may be conditions on Person.comment_tags, Article.comment_tags and/or Comment.tags,
+      # but only Comment.tags will be represented in the through_reflection_chain. So this method
+      # creates an array of conditions corresponding to the through_reflection_chain. Each item in
+      # the through_conditions array corresponds to an item in the through_reflection_chain, and is
+      # itself an array of conditions from an arbitrary number of relevant reflections.
+      def through_conditions
+        @through_conditions ||= begin
+          # Initialize the first item - which corresponds to this reflection - either by recursing
+          # into the souce reflection (if it is itself a through reflection), or by grabbing the
+          # source reflection conditions.
+          if source_reflection.source_reflection
+            conditions = source_reflection.through_conditions
+          else
+            conditions = [Array.wrap(source_reflection.options[:conditions])]
+          end
+          
+          # Add to it the conditions from this reflection if necessary.
+          conditions.first << options[:conditions] if options[:conditions]
+          
+          # Recursively fill out the rest of the array from the through reflection
+          conditions += through_reflection.through_conditions
+          
+          # And return
+          conditions
+        end
+      end
+      
       def nested?
         through_reflection_chain.length > 2
       end

activerecord/test/cases/associations/cascaded_eager_loading_test.rb

@@ -15,7 +15,7 @@ def test_eager_association_loading_with_cascaded_two_levels
     authors = Author.find(:all, :include=>{:posts=>:comments}, :order=>"authors.id")
     assert_equal 3, authors.size
     assert_equal 5, authors[0].posts.size
-    assert_equal 2, authors[1].posts.size
+    assert_equal 3, authors[1].posts.size
     assert_equal 10, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
   end
 
@@ -23,7 +23,7 @@ def test_eager_association_loading_with_cascaded_two_levels_and_one_level
     authors = Author.find(:all, :include=>[{:posts=>:comments}, :categorizations], :order=>"authors.id")
     assert_equal 3, authors.size
     assert_equal 5, authors[0].posts.size
-    assert_equal 2, authors[1].posts.size
+    assert_equal 3, authors[1].posts.size
     assert_equal 10, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
     assert_equal 1, authors[0].categorizations.size
     assert_equal 2, authors[1].categorizations.size
@@ -56,7 +56,7 @@ def test_eager_association_loading_with_cascaded_two_levels_with_two_has_many_as
     authors = Author.find(:all, :include=>{:posts=>[:comments, :categorizations]}, :order=>"authors.id")
     assert_equal 3, authors.size
     assert_equal 5, authors[0].posts.size
-    assert_equal 2, authors[1].posts.size
+    assert_equal 3, authors[1].posts.size
     assert_equal 10, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
   end
 

activerecord/test/cases/associations/eager_test.rb

@@ -53,8 +53,8 @@ def test_loading_conditions_with_or
 
   def test_with_ordering
     list = Post.find(:all, :include => :comments, :order => "posts.id DESC")
-    [:misc_by_mary, :misc_by_bob, :eager_other, :sti_habtm, :sti_post_and_comments,
+    [:other_by_mary, :other_by_bob, :misc_by_mary, :misc_by_bob, :eager_other,
-     :sti_comments, :authorless, :thinking, :welcome
+     :sti_habtm, :sti_post_and_comments, :sti_comments, :authorless, :thinking, :welcome
     ].each_with_index do |post, index|
       assert_equal posts(post), list[index]
     end

activerecord/test/cases/associations/nested_has_many_through_associations_test.rb

@@ -92,8 +92,6 @@ def test_has_many_through_has_many_through_with_has_many_source_reflection
     assert_no_queries do
       assert_equal [luke, david, david], authors.first.subscribers.sort_by(&:nick)
     end
-    
-    # TODO: Add eager loading test using LEFT OUTER JOIN
   end
   
   # has_many through
@@ -325,7 +323,7 @@ def test_distinct_has_many_through_a_has_many_through_association_on_through_ref
   
   def test_nested_has_many_through_with_a_table_referenced_multiple_times
     author = authors(:bob)
-    assert_equal [posts(:misc_by_bob), posts(:misc_by_mary)], author.similar_posts.sort_by(&:id)
+    assert_equal [posts(:misc_by_bob), posts(:misc_by_mary), posts(:other_by_bob), posts(:other_by_mary)], author.similar_posts.sort_by(&:id)
     
     # Mary and Bob both have posts in misc, but they are the only ones.
     authors = Author.joins(:similar_posts).where('posts.id' => posts(:misc_by_bob).id)
@@ -406,6 +404,42 @@ def test_nested_has_one_through_writers_should_raise_error
     end
   end
   
+  def test_nested_has_many_through_with_conditions_on_through_associations
+    blue, bob = tags(:blue), authors(:bob)
+  
+    assert_equal [blue], bob.misc_post_first_blue_tags
+    
+    # Pointless condition to force single-query loading
+    assert_includes_and_joins_equal(
+      Author.where('tags.id = tags.id'),
+      [bob], :misc_post_first_blue_tags
+    )
+    
+    assert Author.where('tags.id' => 100).joins(:misc_post_first_blue_tags).empty?
+    
+    authors = assert_queries(3) { Author.includes(:misc_post_first_blue_tags).to_a }
+    assert_no_queries do
+      assert_equal [blue], authors[2].misc_post_first_blue_tags
+    end
+  end
+  
+  def test_nested_has_many_through_with_conditions_on_source_associations
+    blue, bob = tags(:blue), authors(:bob)
+    
+    assert_equal [blue], bob.misc_post_first_blue_tags_2
+    
+    # Pointless condition to force single-query loading
+    assert_includes_and_joins_equal(
+      Author.where('tags.id = tags.id'),
+      [bob], :misc_post_first_blue_tags_2
+    )
+    
+    authors = assert_queries(4) { Author.includes(:misc_post_first_blue_tags_2).to_a }
+    assert_no_queries do
+      assert_equal [blue], authors[2].misc_post_first_blue_tags_2
+    end
+  end
+  
   private
   
     def assert_includes_and_joins_equal(query, expected, association)

activerecord/test/cases/batches_test.rb

@@ -24,7 +24,7 @@ def test_each_should_raise_if_select_is_set_without_id
   end
 
   def test_each_should_execute_if_id_is_in_select
-    assert_queries(5) do
+    assert_queries(6) do
       Post.find_each(:select => "id, title, type", :batch_size => 2) do |post|
         assert_kind_of Post, post
       end

activerecord/test/cases/finder_test.rb

@@ -123,11 +123,13 @@ def test_find_all_with_prepared_limit_and_offset
   def test_find_all_with_limit_and_offset_and_multiple_order_clauses
     first_three_posts = Post.find :all, :order => 'author_id, id', :limit => 3, :offset => 0
     second_three_posts = Post.find :all, :order => ' author_id,id ', :limit => 3, :offset => 3
-    last_posts = Post.find :all, :order => ' author_id, id  ', :limit => 3, :offset => 6
+    third_three_posts = Post.find :all, :order => ' author_id, id  ', :limit => 3, :offset => 6
+    last_posts = Post.find :all, :order => ' author_id, id  ', :limit => 3, :offset => 9
 
     assert_equal [[0,3],[1,1],[1,2]], first_three_posts.map { |p| [p.author_id, p.id] }
     assert_equal [[1,4],[1,5],[1,6]], second_three_posts.map { |p| [p.author_id, p.id] }
-    assert_equal [[2,7],[2,9],[3,8]], last_posts.map { |p| [p.author_id, p.id] }
+    assert_equal [[2,7],[2,9],[2,11]], third_three_posts.map { |p| [p.author_id, p.id] }
+    assert_equal [[3,8],[3,10]], last_posts.map { |p| [p.author_id, p.id] }
   end
 
 

activerecord/test/cases/relations_test.rb

@@ -501,22 +501,22 @@ def test_relation_merging_with_preload
   def test_count
     posts = Post.scoped
 
-    assert_equal 9, posts.count
+    assert_equal 11, posts.count
-    assert_equal 9, posts.count(:all)
+    assert_equal 11, posts.count(:all)
-    assert_equal 9, posts.count(:id)
+    assert_equal 11, posts.count(:id)
 
     assert_equal 1, posts.where('comments_count > 1').count
-    assert_equal 7, posts.where(:comments_count => 0).count
+    assert_equal 9, posts.where(:comments_count => 0).count
   end
 
   def test_count_with_distinct
     posts = Post.scoped
 
     assert_equal 3, posts.count(:comments_count, :distinct => true)
-    assert_equal 9, posts.count(:comments_count, :distinct => false)
+    assert_equal 11, posts.count(:comments_count, :distinct => false)
 
     assert_equal 3, posts.select(:comments_count).count(:distinct => true)
-    assert_equal 9, posts.select(:comments_count).count(:distinct => false)
+    assert_equal 11, posts.select(:comments_count).count(:distinct => false)
   end
 
   def test_count_explicit_columns
@@ -526,7 +526,7 @@ def test_count_explicit_columns
     assert_equal [0], posts.select('comments_count').where('id is not null').group('id').order('id').count.values.uniq
     assert_equal 0, posts.where('id is not null').select('comments_count').count
 
-    assert_equal 9, posts.select('comments_count').count('id')
+    assert_equal 11, posts.select('comments_count').count('id')
     assert_equal 0, posts.select('comments_count').count
     assert_equal 0, posts.count(:comments_count)
     assert_equal 0, posts.count('comments_count')
@@ -541,12 +541,12 @@ def test_multiple_selects
   def test_size
     posts = Post.scoped
 
-    assert_queries(1) { assert_equal 9, posts.size }
+    assert_queries(1) { assert_equal 11, posts.size }
     assert ! posts.loaded?
 
     best_posts = posts.where(:comments_count => 0)
     best_posts.to_a # force load
-    assert_no_queries { assert_equal 7, best_posts.size }
+    assert_no_queries { assert_equal 9, best_posts.size }
   end
 
   def test_count_complex_chained_relations

activerecord/test/fixtures/posts.yml

@@ -64,3 +64,17 @@ misc_by_mary:
   title: misc post by mary
   body: hello
   type: Post
+
+other_by_bob:
+  id: 10
+  author_id: 3
+  title: other post by bob
+  body: hello
+  type: Post
+
+other_by_mary:
+  id: 11
+  author_id: 2
+  title: other post by mary
+  body: hello
+  type: Post

activerecord/test/fixtures/taggings.yml

@@ -38,3 +38,31 @@ misc_post_by_mary:
   tag_id: 2
   taggable_id: 9
   taggable_type: Post
+
+misc_by_bob_blue_first:
+  id: 8
+  tag_id: 3
+  taggable_id: 8
+  taggable_type: Post
+  comment: first
+
+misc_by_bob_blue_second:
+  id: 9
+  tag_id: 3
+  taggable_id: 8
+  taggable_type: Post
+  comment: second
+
+other_by_bob_blue:
+  id: 10
+  tag_id: 3
+  taggable_id: 10
+  taggable_type: Post
+  comment: first
+
+other_by_mary_blue:
+  id: 11
+  tag_id: 3
+  taggable_id: 11
+  taggable_type: Post
+  comment: first

activerecord/test/fixtures/tags.yml

@@ -5,3 +5,7 @@ general:
 misc:
   id: 2
   name: Misc
+
+blue:
+  id: 3
+  name: Blue

activerecord/test/models/author.rb

@@ -86,7 +86,7 @@ def testing_proxy_target
   has_many :tagging,         :through => :posts
   has_many :taggings,        :through => :posts
   has_many :tags,            :through => :posts
-  has_many :similar_posts,   :through => :tags,  :source => :tagged_posts
+  has_many :similar_posts,   :through => :tags,  :source => :tagged_posts, :uniq => true
   has_many :distinct_tags,   :through => :posts, :source => :tags, :select => "DISTINCT tags.*", :order => "tags.name"
   has_many :post_categories, :through => :posts, :source => :categories
   has_many :tagging_tags,    :through => :taggings, :source => :tag
@@ -103,6 +103,11 @@ def testing_proxy_target
 
   has_many :post_categories, :through => :posts, :source => :categories
   has_many :category_post_comments, :through => :categories, :source => :post_comments
+  
+  has_many :misc_posts, :class_name => 'Post', :conditions => "posts.title LIKE 'misc post%'"
+  has_many :misc_post_first_blue_tags, :through => :misc_posts, :source => :first_blue_tags
+
+  has_many :misc_post_first_blue_tags_2, :through => :posts, :source => :first_blue_tags_2, :conditions => "posts.title LIKE 'misc post%'"
 
   scope :relation_include_posts, includes(:posts)
   scope :relation_include_tags, includes(:tags)

activerecord/test/models/post.rb

@@ -64,6 +64,11 @@ def add_joins_and_select
   has_many :funky_tags, :through => :taggings, :source => :tag
   has_many :super_tags, :through => :taggings
   has_one :tagging, :as => :taggable
+  
+  has_many :first_taggings, :as => :taggable, :class_name => 'Tagging', :conditions => "taggings.comment = 'first'"
+  has_many :first_blue_tags, :through => :first_taggings, :source => :tag, :conditions => "tags.name = 'Blue'"
+
+  has_many :first_blue_tags_2, :through => :taggings, :source => :blue_tag, :conditions => "taggings.comment = 'first'"
 
   has_many :invalid_taggings, :as => :taggable, :class_name => "Tagging", :conditions => 'taggings.id < 0'
   has_many :invalid_tags, :through => :invalid_taggings, :source => :tag

activerecord/test/models/tagging.rb

@@ -6,5 +6,6 @@ class Tagging < ActiveRecord::Base
   belongs_to :tag, :include => :tagging
   belongs_to :super_tag,   :class_name => 'Tag', :foreign_key => 'super_tag_id'
   belongs_to :invalid_tag, :class_name => 'Tag', :foreign_key => 'tag_id'
+  belongs_to :blue_tag,    :class_name => 'Tag', :foreign_key => :tag_id, :conditions => "tags.name = 'Blue'"
   belongs_to :taggable, :polymorphic => true, :counter_cache => true
-end
+end

activerecord/test/schema/schema.rb

@@ -537,6 +537,7 @@ def create_table(*args, &block)
     t.column :super_tag_id, :integer
     t.column :taggable_type, :string
     t.column :taggable_id, :integer
+    t.string :comment
   end
 
   create_table :tags, :force => true do |t|