1 files changed, 81 insertions, 27 deletions

diff --git a/activerecord/lib/active_record/associations/through_association_scope.rb b/activerecord/lib/active_record/associations/through_association_scope.rb
index cabb33c4a8..90ebadda89 100644
--- a/activerecord/lib/active_record/associations/through_association_scope.rb
+++ b/activerecord/lib/active_record/associations/through_association_scope.rb
@@ -1,3 +1,5 @@
+require 'enumerator'
+
 module ActiveRecord
   # = Active Record Through Association Scope
   module Associations
@@ -19,9 +21,9 @@ module ActiveRecord
 
       # Build SQL conditions from attributes, qualified by table name.
       def construct_conditions
-        table_name = @reflection.through_reflection.quoted_table_name
-        conditions = construct_quoted_owner_attributes(@reflection.through_reflection).map do |attr, value|
-          "#{table_name}.#{attr} = #{value}"
+        reflection = @reflection.through_reflection_chain.last
+        conditions = construct_quoted_owner_attributes(reflection).map do |attr, value|
+          "#{table_aliases[reflection]}.#{attr} = #{value}"
         end
         conditions << sql_conditions if sql_conditions
         "(" + conditions.join(') AND (') + ")"
@@ -49,35 +51,87 @@ module ActiveRecord
         distinct = "DISTINCT " if @reflection.options[:uniq]
         selected = custom_select || @reflection.options[:select] || "#{distinct}#{@reflection.quoted_table_name}.*"
       end
-
+      
       def construct_joins(custom_joins = nil)
-        polymorphic_join = nil
-        if @reflection.source_reflection.macro == :belongs_to
-          reflection_primary_key = @reflection.klass.primary_key
-          source_primary_key     = @reflection.source_reflection.primary_key_name
-          if @reflection.options[:source_type]
-            polymorphic_join = "AND %s.%s = %s" % [
-              @reflection.through_reflection.quoted_table_name, "#{@reflection.source_reflection.options[:foreign_type]}",
-              @owner.class.quote_value(@reflection.options[:source_type])
-            ]
+        # puts @reflection.through_reflection_chain.map(&:inspect)
+        
+        "#{construct_through_joins} #{@reflection.options[:joins]} #{custom_joins}"
+      end
+
+      def construct_through_joins
+        joins = []
+        
+        # Iterate over each pair in the through reflection chain, joining them together
+        @reflection.through_reflection_chain.each_cons(2) do |left, right|
+          polymorphic_join  = nil
+          
+          case
+            when left.source_reflection.nil?
+              left_primary_key  = left.primary_key_name
+              right_primary_key = right.klass.primary_key
+              
+              if left.options[:as]
+                polymorphic_join = "AND %s.%s = %s" % [
+                  table_aliases[left], "#{left.options[:as]}_type",
+                  @owner.class.quote_value(right.klass.name)
+                ]
+              end
+            when left.source_reflection.macro == :belongs_to
+              left_primary_key  = left.klass.primary_key
+              right_primary_key = left.source_reflection.primary_key_name
+              
+              if left.options[:source_type]
+                polymorphic_join = "AND %s.%s = %s" % [
+                  table_aliases[right],
+                  left.source_reflection.options[:foreign_type].to_s,
+                  @owner.class.quote_value(left.options[:source_type])
+                ]
+              end
+            else
+              left_primary_key  = left.source_reflection.primary_key_name
+              right_primary_key = right.klass.primary_key
+              
+              if left.source_reflection.options[:as]
+                polymorphic_join = "AND %s.%s = %s" % [
+                  table_aliases[left],
+                  "#{left.source_reflection.options[:as]}_type",
+                  @owner.class.quote_value(right.klass.name)
+                ]
+              end
           end
-        else
-          reflection_primary_key = @reflection.source_reflection.primary_key_name
-          source_primary_key     = @reflection.through_reflection.klass.primary_key
-          if @reflection.source_reflection.options[:as]
-            polymorphic_join = "AND %s.%s = %s" % [
-              @reflection.quoted_table_name, "#{@reflection.source_reflection.options[:as]}_type",
-              @owner.class.quote_value(@reflection.through_reflection.klass.name)
-            ]
+          
+          if right.quoted_table_name == table_aliases[right]
+            table = right.quoted_table_name
+          else
+            table = "#{right.quoted_table_name} #{table_aliases[right]}"
           end
+          
+          joins << "INNER JOIN %s ON %s.%s = %s.%s %s" % [
+            table,
+            table_aliases[left],  left_primary_key,
+            table_aliases[right], right_primary_key,
+            polymorphic_join
+          ]
         end
+        
+        joins.join(" ")
+      end
 
-        "INNER JOIN %s ON %s.%s = %s.%s %s #{@reflection.options[:joins]} #{custom_joins}" % [
-          @reflection.through_reflection.quoted_table_name,
-          @reflection.quoted_table_name, reflection_primary_key,
-          @reflection.through_reflection.quoted_table_name, source_primary_key,
-          polymorphic_join
-        ]
+      def table_aliases
+        @table_aliases ||= begin
+          tally = {}
+          @reflection.through_reflection_chain.inject({}) do |aliases, reflection|
+            if tally[reflection.table_name].nil?
+              tally[reflection.table_name] = 1
+              aliases[reflection] = reflection.quoted_table_name
+            else
+              tally[reflection.table_name] += 1
+              aliased_table_name = reflection.table_name + "_#{tally[reflection.table_name]}"
+              aliases[reflection] = reflection.klass.connection.quote_table_name(aliased_table_name)
+            end
+            aliases
+          end
+        end
       end
 
       # Construct attributes for associate pointing to owner.