15 files changed, 130 insertions, 11 deletions
diff --git a/lib/arel/algebra/extensions/array.rb b/lib/arel/algebra/extensions/array.rb
index 5b6d6d6abd..935569a07b 100644
--- a/lib/arel/algebra/extensions/array.rb
+++ b/lib/arel/algebra/extensions/array.rb
@@ -2,4 +2,11 @@ class Array
   def to_hash
     Hash[*flatten]
   end
+  
+  def group_by
+    inject({}) do |groups, element|
+      (groups[yield(element)] ||= []) << element
+      groups
+    end
+  end
 end
 \ No newline at end of file
diff --git a/lib/arel/algebra/extensions/hash.rb b/lib/arel/algebra/extensions/hash.rb
index 7472b5aa73..bc97785e62 100644
--- a/lib/arel/algebra/extensions/hash.rb
+++ b/lib/arel/algebra/extensions/hash.rb
@@ -4,4 +4,11 @@ class Hash
       bound.merge(key.bind(relation) => value.bind(relation))
     end
   end
+  
+  def slice(*attributes)
+    inject({}) do |cheese, (key, value)|
+      cheese[key] = value if attributes.include?(key)
+      cheese
+    end
+  end
 end
 \ No newline at end of file
diff --git a/lib/arel/algebra/extensions/object.rb b/lib/arel/algebra/extensions/object.rb
index d626407dcb..efdbbf525f 100644
--- a/lib/arel/algebra/extensions/object.rb
+++ b/lib/arel/algebra/extensions/object.rb
@@ -12,4 +12,9 @@ class Object
       self
     end
   end
+
+  def let
+    yield(self)
+  end
 end
+
diff --git a/lib/arel/algebra/primitives.rb b/lib/arel/algebra/primitives.rb
index a4c3169e0b..df8d16a5d5 100644
--- a/lib/arel/algebra/primitives.rb
+++ b/lib/arel/algebra/primitives.rb
@@ -1,4 +1,5 @@
 require 'arel/algebra/primitives/attribute'
+require 'arel/algebra/primitives/ordering'
 require 'arel/algebra/primitives/value'
 require 'arel/algebra/primitives/expression'
 
diff --git a/lib/arel/algebra/primitives/attribute.rb b/lib/arel/algebra/primitives/attribute.rb
index 943c5b030e..7a4411e248 100644
--- a/lib/arel/algebra/primitives/attribute.rb
+++ b/lib/arel/algebra/primitives/attribute.rb
@@ -17,6 +17,10 @@ module Arel
     def aggregation?
       false
     end
+    
+    def inspect
+      "<Attribute #{name}>"
+    end
 
     module Transformations
       def self.included(klass)
@@ -129,5 +133,18 @@ module Arel
       end
     end
     include Expressions
+    
+    module Orderings
+      def asc
+        Ascending.new(self)
+      end
+      
+      def desc
+        Descending.new(self)
+      end
+      
+      alias_method :to_ordering, :asc
+    end
+    include Orderings
   end
 end
diff --git a/lib/arel/algebra/primitives/ordering.rb b/lib/arel/algebra/primitives/ordering.rb
new file mode 100644
index 0000000000..e8d8f97188
--- /dev/null
+++ b/lib/arel/algebra/primitives/ordering.rb
@@ -0,0 +1,18 @@
+module Arel
+  class Ordering
+    attributes :attribute
+    deriving :initialize, :==
+    delegate :relation, :to => :attribute
+    
+    def bind(relation)
+      self.class.new(attribute.bind(relation))
+    end
+    
+    def to_ordering
+      self
+    end
+  end
+  
+  class Ascending  < Ordering; end
+  class Descending < Ordering; end
+end
+\ No newline at end of file
diff --git a/lib/arel/algebra/primitives/value.rb b/lib/arel/algebra/primitives/value.rb
index 76c82890d0..e363805140 100644
--- a/lib/arel/algebra/primitives/value.rb
+++ b/lib/arel/algebra/primitives/value.rb
@@ -7,12 +7,8 @@ module Arel
       Value.new(value, relation)
     end
 
-    def aggregation?
-      false
-    end
-
-    def to_attribute
-      value
+    def to_ordering
+      self
     end
   end
 end
diff --git a/lib/arel/algebra/relations/operations/order.rb b/lib/arel/algebra/relations/operations/order.rb
index 05af3fde4d..eccd8bcda0 100644
--- a/lib/arel/algebra/relations/operations/order.rb
+++ b/lib/arel/algebra/relations/operations/order.rb
@@ -10,7 +10,8 @@ module Arel
 
     # TESTME
     def orders
-      (orderings + relation.orders).collect { |o| o.bind(self) }
+      # QUESTION - do we still need relation.orders ?
+      (orderings + relation.orders).collect { |o| o.bind(self) }.collect { |o| o.to_ordering }
     end
   end
 end
 \ No newline at end of file
diff --git a/lib/arel/engines/memory/primitives.rb b/lib/arel/engines/memory/primitives.rb
index 77d4c1a52c..f8bbcedb55 100644
--- a/lib/arel/engines/memory/primitives.rb
+++ b/lib/arel/engines/memory/primitives.rb
@@ -10,4 +10,18 @@ module Arel
       value
     end
   end
+  
+  class Ordering
+    def eval(row1, row2)
+      (attribute.eval(row1) <=> attribute.eval(row2)) * direction
+    end
+  end
+  
+  class Descending < Ordering
+    def direction; -1 end
+  end
+  
+  class Ascending < Ordering
+    def direction; 1 end
+  end
 end
 \ No newline at end of file
diff --git a/lib/arel/engines/memory/relations.rb b/lib/arel/engines/memory/relations.rb
index 9f8264c439..1b009537b9 100644
--- a/lib/arel/engines/memory/relations.rb
+++ b/lib/arel/engines/memory/relations.rb
@@ -1,3 +1,4 @@
 require 'arel/engines/memory/relations/array'
 require 'arel/engines/memory/relations/operations'
+require 'arel/engines/memory/relations/compound'
 
diff --git a/lib/arel/engines/memory/relations/compound.rb b/lib/arel/engines/memory/relations/compound.rb
new file mode 100644
index 0000000000..b029082d57
--- /dev/null
+++ b/lib/arel/engines/memory/relations/compound.rb
@@ -0,0 +1,5 @@
+module Arel
+  class Compound < Relation
+    delegate :array, :to => :relation
+  end
+end
diff --git a/lib/arel/engines/memory/relations/operations.rb b/lib/arel/engines/memory/relations/operations.rb
index eb11fb55fd..115df054df 100644
--- a/lib/arel/engines/memory/relations/operations.rb
+++ b/lib/arel/engines/memory/relations/operations.rb
@@ -4,4 +4,37 @@ module Arel
       relation.eval.select { |row| predicate.eval(row) }
     end
   end
+  
+  class Order < Compound
+    def eval
+      relation.eval.sort do |row1, row2|
+        ordering = orderings.detect { |o| o.eval(row1, row2) != 0 } || orderings.last
+        ordering.eval(row1, row2)
+      end
+    end
+  end
+  
+  class Project < Compound
+    def eval
+      relation.eval.collect { |r| r.slice(*projections) }
+    end
+  end
+  
+  class Take < Compound
+    def eval
+      relation.eval[0, taken]
+    end
+  end
+  
+  class Skip < Compound
+    def eval
+      relation.eval[skipped..-1]
+    end
+  end
+  
+  class Group < Compound
+    def eval
+      raise NotImplementedError
+    end
+  end
 end
 \ No newline at end of file
diff --git a/lib/arel/engines/sql/formatters.rb b/lib/arel/engines/sql/formatters.rb
index f82ddf631f..bc5f0f7c64 100644
--- a/lib/arel/engines/sql/formatters.rb
+++ b/lib/arel/engines/sql/formatters.rb
@@ -47,9 +47,9 @@ module Arel
     class WhereClause < PassThrough
     end
 
-    class OrderClause < PassThrough
-      def attribute(attribute)
-        "#{quote_table_name(name_for(attribute.original_relation))}.#{quote_column_name(attribute.name)}"
+    class OrderClause < PassThrough      
+      def ordering(ordering)
+        "#{quote_table_name(name_for(ordering.attribute.original_relation))}.#{quote_column_name(ordering.attribute.name)} #{ordering.direction_sql}"
       end
     end
 
diff --git a/lib/arel/engines/sql/primitives.rb b/lib/arel/engines/sql/primitives.rb
index 6f89723afe..9e9143ac0f 100644
--- a/lib/arel/engines/sql/primitives.rb
+++ b/lib/arel/engines/sql/primitives.rb
@@ -24,6 +24,20 @@ module Arel
       object.to_sql(Sql::Value.new(relation))
     end
   end
+  
+  class Ordering
+    def to_sql(formatter = Sql::OrderClause.new(relation))
+      formatter.ordering self
+    end
+  end
+  
+  class Ascending < Ordering
+    def direction_sql; 'ASC' end
+  end
+  
+  class Descending < Ordering
+    def direction_sql; 'DESC' end
+  end
 
   class Expression < Attribute
     def to_sql(formatter = Sql::SelectClause.new(relation))
diff --git a/lib/arel/engines/sql/relations/utilities/compound.rb b/lib/arel/engines/sql/relations/utilities/compound.rb
index 502bf8b01e..61df196d6e 100644
--- a/lib/arel/engines/sql/relations/utilities/compound.rb
+++ b/lib/arel/engines/sql/relations/utilities/compound.rb
@@ -1,6 +1,6 @@
 module Arel
   class Compound < Relation
-    delegate :table, :table_sql, :array, :to => :relation
+    delegate :table, :table_sql, :to => :relation
   end
 end
     
 \ No newline at end of file