1 files changed, 24 insertions, 0 deletions
diff --git a/lib/arel/algebra/relations/utilities/externalization.rb b/lib/arel/algebra/relations/utilities/externalization.rb
new file mode 100644
index 0000000000..13758ccec9
--- /dev/null
+++ b/lib/arel/algebra/relations/utilities/externalization.rb
@@ -0,0 +1,24 @@
+module Arel
+  class Externalization < Compound
+    attributes :relation
+    deriving :initialize, :==
+
+    def wheres
+      []
+    end
+
+    def attributes
+      @attributes ||= relation.attributes.collect { |a| a.to_attribute(self) }
+    end
+  end
+
+  class Relation
+    def externalize
+      @externalized ||= externalizable?? Externalization.new(self) : self
+    end
+
+    def externalizable?
+      false
+    end
+  end
+end