* Denormalized post versions. Testing has shown it reduces the size

of the table 66%.

db/migrate/20100205163027_create_post_histories.rb

@@ -0,0 +1,16 @@
+class CreatePostHistories < ActiveRecord::Migration
+  def self.up
+    create_table :post_histories do |t|
+      t.timestamps
+      
+      t.column :post_id, :integer, :null => false
+      t.column :revisions, :text, :null => false
+    end
+    
+    add_index :post_histories, :post_id
+  end
+
+  def self.down
+    drop_table :post_histories
+  end
+end