1 files changed, 40 insertions, 0 deletions
diff --git a/lib/arel/relations/utilities/aggregation.rb b/lib/arel/relations/utilities/aggregation.rb
new file mode 100644
index 0000000000..66150bff0a
--- /dev/null
+++ b/lib/arel/relations/utilities/aggregation.rb
@@ -0,0 +1,40 @@
+module Arel
+  class Aggregation < Compound
+    include Recursion::BaseCase
+
+    def initialize(relation)
+      @relation = relation
+    end
+    
+    def wheres
+      []
+    end
+  
+    def table_sql(formatter = Sql::TableReference.new(relation))
+      formatter.select relation.select_sql, self
+    end
+  
+    def attributes
+      @attributes ||= relation.attributes.collect(&:to_attribute).collect { |a| a.bind(self) }
+    end
+    
+    def name
+      relation.name + '_aggregation'
+    end
+    
+    def ==(other)
+      Aggregation   === other and
+      self.relation ==  other.relation
+    end
+  end
+  
+  class Relation
+    def externalize
+      @externalized ||= aggregation?? Aggregation.new(self) : self
+    end
+    
+    def aggregation?
+      false
+    end
+  end
+end
+\ No newline at end of file