About 85% through porting over MySQL on duplicate key functionality.

test/models/topic.rb

@@ -1,6 +1,7 @@
 class Topic < ActiveRecord::Base
   validates_presence_of :author_name
   has_many :books
+  belongs_to :parent, :class_name => "Topic"
   
   composed_of :description, :mapping => [ %w(title title), %w(author_name author_name)], :allow_nil => true, :class_name => "TopicDescription"
 end