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class AddActsAsTaggableTables < ActiveRecord::Migration 
  def self.up 
    create_table :tags do |t| 
      t.column :name, :string
      t.column :taggings_count, :integer, :default => 0, :null => false
    end 
    add_index :tags, :name 
    add_index :tags, :taggings_count

    create_table :taggings do |t| 
      t.column :tag_id, :integer 
      t.column :taggable_id, :integer 
      t.column :taggable_type, :string
      t.column :user_id, :integer
    end     

    # Find objects for a tag
    add_index :taggings, [:tag_id, :taggable_type] 
    add_index :taggings, [:user_id, :tag_id, :taggable_type]
    # Find tags for an object 
    add_index :taggings, [:taggable_id, :taggable_type] 
    add_index :taggings, [:user_id, :taggable_id, :taggable_type]
  end 

  def self.down 
    drop_table :tags 
    drop_table :taggings 
  end 
end