9 files changed, 91 insertions, 16 deletions
diff --git a/lib/active_relation/primitives/aggregation.rb b/lib/active_relation/primitives/aggregation.rb
index 48f8946835..26348fb35e 100644
--- a/lib/active_relation/primitives/aggregation.rb
+++ b/lib/active_relation/primitives/aggregation.rb
@@ -6,6 +6,10 @@ module ActiveRelation
       @attribute, @function_sql = attribute, function_sql
     end
 
+    def substitute(new_relation)
+      Aggregation.new(attribute.substitute(new_relation), function_sql)
+    end
+    
     def to_sql(strategy = nil)
       "#{function_sql}(#{attribute.to_sql})"
     end
diff --git a/lib/active_relation/primitives/attribute.rb b/lib/active_relation/primitives/attribute.rb
index 90bbe8012b..eb167b1a66 100644
--- a/lib/active_relation/primitives/attribute.rb
+++ b/lib/active_relation/primitives/attribute.rb
@@ -6,18 +6,25 @@ module ActiveRelation
       @relation, @name, @alias = relation, name, aliaz
     end
 
-    def as(aliaz = nil)
-      Attribute.new(relation, name, aliaz)
-    end
+    module Transformations
+      def as(aliaz = nil)
+        Attribute.new(relation, name, aliaz)
+      end
+    
+      def substitute(new_relation)
+        Attribute.new(new_relation, name, @alias)
+      end
 
+      def qualify
+        self.as(qualified_name)
+      end
+    end
+    include Transformations
+    
     def qualified_name
       "#{relation.name}.#{name}"
     end
 
-    def qualify
-      self.as(qualified_name)
-    end
-
     def ==(other)
       relation == other.relation and name == other.name and @alias == other.alias
     end
diff --git a/lib/active_relation/relations.rb b/lib/active_relation/relations.rb
index 9ae8f16524..c9b9de93b2 100644
--- a/lib/active_relation/relations.rb
+++ b/lib/active_relation/relations.rb
@@ -2,6 +2,8 @@ require 'active_relation/relations/relation'
 require 'active_relation/relations/compound'
 require 'active_relation/relations/table'
 require 'active_relation/relations/join'
+require 'active_relation/relations/schmoin'
+require 'active_relation/relations/group'
 require 'active_relation/relations/projection'
 require 'active_relation/relations/selection'
 require 'active_relation/relations/order'
diff --git a/lib/active_relation/relations/alias.rb b/lib/active_relation/relations/alias.rb
index 63a92ccba1..f40e51475e 100644
--- a/lib/active_relation/relations/alias.rb
+++ b/lib/active_relation/relations/alias.rb
@@ -8,7 +8,7 @@ module ActiveRelation
     end
       
     def attributes
-      relation.attributes.collect(&method(:substitute))
+      relation.attributes.collect { |attribute| attribute.substitute(self) }
     end
 
     def ==(other)
@@ -22,13 +22,8 @@ module ActiveRelation
     
     def attribute(name)
       if unaliased_attribute = relation[name]
-        substitute(unaliased_attribute)
+        unaliased_attribute.substitute(self)
       end
     end
-    
-    private
-    def substitute(attribute)
-      Attribute.new(self, attribute.name, attribute.alias)
-    end
   end
 end
 \ No newline at end of file
diff --git a/lib/active_relation/relations/compound.rb b/lib/active_relation/relations/compound.rb
index d6da8eb8fa..bbc7ff1bae 100644
--- a/lib/active_relation/relations/compound.rb
+++ b/lib/active_relation/relations/compound.rb
@@ -2,6 +2,7 @@ module ActiveRelation
   class Compound < Relation
     attr_reader :relation
 
-    delegate :attributes, :attribute, :joins, :selects, :orders, :table_sql, :inserts, :limit, :offset, :to => :relation
+    delegate :attributes, :attribute, :joins, :selects, :orders, :groupings, :table_sql, :inserts, :limit, :offset,
+             :to => :relation
   end
 end
 \ No newline at end of file
diff --git a/lib/active_relation/relations/group.rb b/lib/active_relation/relations/group.rb
new file mode 100644
index 0000000000..bc363970c7
--- /dev/null
+++ b/lib/active_relation/relations/group.rb
@@ -0,0 +1,17 @@
+module ActiveRelation
+  class Group < Compound
+    attr_reader :groupings
+
+    def initialize(relation, *groupings)
+      @relation, @groupings = relation, groupings
+    end
+
+    def ==(other)
+      relation == other.relation and groupings == other.groupings
+    end
+
+    def qualify
+      Group.new(relation.qualify, *groupings.collect(&:qualify))
+    end
+  end
+end
+\ No newline at end of file
diff --git a/lib/active_relation/relations/order.rb b/lib/active_relation/relations/order.rb
index d5c2a54cd1..688207f7a9 100644
--- a/lib/active_relation/relations/order.rb
+++ b/lib/active_relation/relations/order.rb
@@ -11,7 +11,7 @@ module ActiveRelation
     end
 
     def qualify
-      Order.new(relation.qualify, *orders.collect { |o| o.qualify })
+      Order.new(relation.qualify, *orders.collect(&:qualify))
     end
   end
 end
 \ No newline at end of file
diff --git a/lib/active_relation/relations/relation.rb b/lib/active_relation/relations/relation.rb
index 663450e69c..18ba5491b1 100644
--- a/lib/active_relation/relations/relation.rb
+++ b/lib/active_relation/relations/relation.rb
@@ -64,6 +64,10 @@ module ActiveRelation
       def delete
         Deletion.new(self)
       end
+      
+      def group(*attributes)
+        Group.new(self, *attributes)
+      end
   
       JoinOperation = Struct.new(:join_sql, :relation1, :relation2) do
         def on(*predicates)
@@ -80,6 +84,7 @@ module ActiveRelation
         (joins unless joins.blank?),
         ("WHERE #{selects.collect{|s| s.to_sql(Sql::Predicate.new)}.join("\n\tAND ")}" unless selects.blank?),
         ("ORDER BY #{orders.collect(&:to_sql)}" unless orders.blank?),
+        ("GROUP BY #{groupings.collect(&:to_sql)}" unless groupings.blank?),
         ("LIMIT #{limit.to_sql}" unless limit.blank?),
         ("OFFSET #{offset.to_sql}" unless offset.blank?)
       ].compact.join("\n")
@@ -95,6 +100,7 @@ module ActiveRelation
     def selects;    []  end
     def orders;     []  end
     def inserts;    []  end
+    def groupings;  []  end
     def joins;      nil end
     def limit;      nil end
     def offset;     nil end
diff --git a/lib/active_relation/relations/schmoin.rb b/lib/active_relation/relations/schmoin.rb
new file mode 100644
index 0000000000..398cfb7b28
--- /dev/null
+++ b/lib/active_relation/relations/schmoin.rb
@@ -0,0 +1,43 @@
+module ActiveRelation
+  class Schmoin < Relation
+    attr_reader :join_sql, :relation1, :relation2, :predicates
+
+    def initialize(join_sql, relation1, relation2, *predicates)
+      @join_sql, @relation1, @relation2, @predicates = join_sql, relation1, relation2, predicates
+    end
+
+    def ==(other)
+      predicates == other.predicates and
+        ((relation1 == other.relation1 and relation2 == other.relation2) or
+        (relation2 == other.relation1 and relation1 == other.relation2))
+    end
+
+    def qualify
+      Schmoin.new(join_sql, relation1.qualify, relation2.qualify, *predicates.collect(&:qualify))
+    end
+
+    protected
+    def joins
+      [relation1.joins, relation2.joins, join].compact.join(" ")
+    end
+
+    def selects
+      relation1.send(:selects) + relation2.send(:selects)
+    end
+
+    def attributes
+      relation1.attributes + relation2.attributes
+    end
+
+    def attribute(name)
+      relation1[name] || relation2[name]
+    end
+
+    delegate :table_sql, :to => :relation1
+
+    private
+    def join
+      "#{join_sql} #{relation2.send(:table_sql)} ON #{predicates.collect { |p| p.to_sql(Sql::Predicate.new) }.join(' AND ')}"
+    end
+  end
+end
+\ No newline at end of file