4 files changed, 76 insertions, 6 deletions
diff --git a/lib/arel/algebra/attributes/attribute.rb b/lib/arel/algebra/attributes/attribute.rb
index 9206b228c8..8a7993f284 100644
--- a/lib/arel/algebra/attributes/attribute.rb
+++ b/lib/arel/algebra/attributes/attribute.rb
@@ -270,5 +270,17 @@ module Arel
       end
     end
     include Types
+
+    def column
+      original_relation.column_for(self)
+    end
+
+    def format(object)
+      object.to_sql(Sql::Attribute.new(self))
+    end
+
+    def to_sql(formatter = Sql::WhereCondition.new(relation))
+      formatter.attribute self
+    end
   end
 end
diff --git a/lib/arel/algebra/expression.rb b/lib/arel/algebra/expression.rb
index 183de3c005..5a93ca9735 100644
--- a/lib/arel/algebra/expression.rb
+++ b/lib/arel/algebra/expression.rb
@@ -16,6 +16,10 @@ module Arel
       true
     end
 
+    def to_sql(formatter = Sql::SelectClause.new(relation))
+      formatter.expression self
+    end
+
     module Transformations
       def as(aliaz)
         self.class.new(attribute, aliaz, self)
@@ -32,11 +36,28 @@ module Arel
     include Transformations
   end
 
-  class Count    < Expression; end
-  class Distinct < Expression; end
-  class Sum      < Expression; end
-  class Maximum  < Expression; end
-  class Minimum  < Expression; end
-  class Average  < Expression; end
+  class Count < Expression
+    def function_sql; 'COUNT' end
+  end
+
+  class Distinct < Expression
+    def function_sql; 'DISTINCT' end
+  end
+
+  class Sum < Expression
+    def function_sql; 'SUM' end
+  end
+
+  class Maximum < Expression
+    def function_sql; 'MAX' end
+  end
+
+  class Minimum < Expression
+    def function_sql; 'MIN' end
+  end
+
+  class Average < Expression
+    def function_sql; 'AVG' end
+  end
 end
 
diff --git a/lib/arel/algebra/ordering.rb b/lib/arel/algebra/ordering.rb
index 984327aaf7..8ed3e1e6e6 100644
--- a/lib/arel/algebra/ordering.rb
+++ b/lib/arel/algebra/ordering.rb
@@ -13,10 +13,23 @@ module Arel
     def == other
       super || (self.class === other && attribute == other.attribute)
     end
+
+    def eval(row1, row2)
+      (attribute.eval(row1) <=> attribute.eval(row2)) * direction
+    end
+
+    def to_sql(formatter = Sql::OrderClause.new(relation))
+      formatter.ordering self
+    end
   end
 
   class Ascending  < Ordering
+    def direction; 1 end
+    def direction_sql; 'ASC' end
   end
+
   class Descending < Ordering
+    def direction_sql; 'DESC' end
+    def direction; -1 end
   end
 end
diff --git a/lib/arel/algebra/value.rb b/lib/arel/algebra/value.rb
index d9fc2e061c..90787fa5ea 100644
--- a/lib/arel/algebra/value.rb
+++ b/lib/arel/algebra/value.rb
@@ -21,5 +21,29 @@ module Arel
     def to_ordering
       self
     end
+
+    def inclusion_predicate_sql
+      value.inclusion_predicate_sql
+    end
+
+    def exclusion_predicate_sql
+      value.exclusion_predicate_sql
+    end
+
+    def equality_predicate_sql
+      value.equality_predicate_sql
+    end
+
+    def inequality_predicate_sql
+      value.inequality_predicate_sql
+    end
+
+    def to_sql(formatter = Sql::WhereCondition.new(relation))
+      formatter.value value
+    end
+
+    def format(object)
+      object.to_sql(Sql::Value.new(relation))
+    end
   end
 end