Add missing unique indices

README.md

@@ -46,6 +46,10 @@ rails generate acts_as_taggable_on:migration
 rake db:migrate
 ```
 
+#### Upgrading
+
+see [UPGRADING](UPGRADING)
+
 ## Testing
 
 Acts As Taggable On uses RSpec for its test coverage. Inside the gem

UPGRADING

@@ -0,0 +1,7 @@
+When upgrading
+
+Re-run the migrations generator
+
+    rake railties:install:migrations FROM=acts_as_taggable_on_engine db:migrate
+
+It will create any new migrations and skip existing ones

db/migrate/2_add_missing_unique_indices.rb

@@ -0,0 +1,21 @@
+class AddMissingUniqueIndices < ActiveRecord::Migration
+
+  def self.up
+    add_index :tags, :name, unique: true
+
+    remove_index :taggings, :tag_id
+    remove_index :taggings, [:taggable_id, :taggable_type, :context]
+    add_index :taggings,
+      [:tag_id, :taggable_id, :taggable_type, :context, :tagger_id, :tagger_type],
+      unique: true, name: 'taggings_idx'
+   end
+
+  def self.down
+    remove_index :tags, :name
+
+    remove_index :taggings, name: 'tagging_idx'
+    add_index :taggings, :tag_id
+    add_index :taggings, [:taggable_id, :taggable_type, :context]
+  end
+
+end

lib/acts-as-taggable-on.rb

@@ -48,6 +48,7 @@ def self.setup
 require "acts_as_taggable_on/tag_list"
 require "acts_as_taggable_on/tags_helper"
 require "acts_as_taggable_on/tagging"
+require 'acts_as_taggable_on/engine'
 
 ActiveSupport.on_load(:active_record) do
   extend ActsAsTaggableOn::Compatibility
@@ -57,4 +58,3 @@ def self.setup
 ActiveSupport.on_load(:action_view) do
   include ActsAsTaggableOn::TagsHelper
 end
-

lib/acts_as_taggable_on/engine.rb

@@ -0,0 +1,6 @@
+require 'rails/engine'
+module ActsAsTaggableOn
+  class Engine < Rails::Engine
+
+  end
+end