basic rename functionality

lib/sql_algebra.rb

@@ -17,6 +17,7 @@ require 'sql_algebra/relations/projection_relation'
 require 'sql_algebra/relations/selection_relation'
 require 'sql_algebra/relations/order_relation'
 require 'sql_algebra/relations/range_relation'
+require 'sql_algebra/relations/rename_relation'
 require 'sql_algebra/relations/join'
 
 require 'sql_algebra/predicates/predicate'

lib/sql_algebra/relations/attribute.rb

@@ -5,6 +5,10 @@ class Attribute
     @relation, @attribute_name, @aliaz = relation, attribute_name, aliaz
   end
   
+  def aliazz(aliaz)
+    Attribute.new(relation, attribute_name, aliaz)
+  end
+  
   def eql?(other)
     relation == other.relation and attribute_name == other.attribute_name
   end

lib/sql_algebra/relations/relation.rb

@@ -32,6 +32,10 @@ class Relation
     def order(*attributes)
       OrderRelation.new(self, *attributes)
     end
+    
+    def rename(attribute, aliaz)
+      RenameRelation.new(self, attribute, aliaz)
+    end
   end
   include Operations
   

spec/relations/attribute_spec.rb

@@ -6,6 +6,12 @@ describe Attribute do
     @relation2 = TableRelation.new(:bar)
   end
   
+  describe 'aliaz' do
+    it "manufactures an aliased attributed" do
+      pending
+    end
+  end
+  
   describe '#eql?' do
     it "obtains if the relation and attribute name are identical" do
       Attribute.new(@relation1, :attribute_name).should be_eql(Attribute.new(@relation1, :attribute_name))

spec/relations/relation_spec.rb

@@ -48,6 +48,12 @@ describe Relation do
     end
   end
   
+  describe Relation, '#rename' do
+    it "manufactures a rename relation" do
+      @relation1.rename(@attribute1, :foo).should == RenameRelation.new(@relation1, @attribute1, :foo)
+    end
+  end
+  
   describe Relation, '#select' do
     before do
       @predicate = EqualityPredicate.new(@attribute1, @attribute2)

spec/relations/table_relation_spec.rb

@@ -1,13 +1,21 @@
 require File.join(File.dirname(__FILE__), '..', 'spec_helper')
 
-describe TableRelation, '#to_sql' do
-  it "returns a simple SELECT query" do
-    TableRelation.new(:users).to_sql.should == SelectBuilder.new do |s|
-      select do
-        column :users, :name
-        column :users, :id
+describe TableRelation do
+  describe '#to_sql' do
+    it "returns a simple SELECT query" do
+      TableRelation.new(:users).to_sql.should == SelectBuilder.new do |s|
+        select do
+          column :users, :name
+          column :users, :id
+        end
+        from :users
       end
-      from :users
     end
   end
-end
+  
+  describe '#attributes' do
+    it 'manufactures attributes corresponding to columns in the table' do
+      pending
+    end
+  end
+end