Add null false on tag_followings fields

db/migrate/20110701215925_create_tag_followings.rb

@@ -1,8 +1,8 @@
 class CreateTagFollowings < ActiveRecord::Migration
   def self.up
     create_table :tag_followings do |t|
-      t.integer :tag_id
-      t.integer :user_id
+      t.integer :tag_id, :null => false
+      t.integer :user_id, :null => false
 
       t.timestamps
     end

db/schema.rb

@@ -327,8 +327,8 @@ ActiveRecord::Schema.define(:version => 20110705003445) do
   add_index "services", ["user_id"], :name => "index_services_on_user_id"
 
   create_table "tag_followings", :force => true do |t|
-    t.integer  "tag_id"
-    t.integer  "user_id"
+    t.integer  "tag_id",     :null => false
+    t.integer  "user_id",    :null => false
     t.datetime "created_at"
     t.datetime "updated_at"
   end