fohow_admin/db/migrate/20121201032356_create_version_associations.rb

# This migration and AddTransactionIdColumnToVersions provide the necessary
# schema for tracking associations.
class CreateVersionAssociations < ActiveRecord::Migration
  def self.up
    create_table :version_associations do |t|
      t.integer  :version_id
      t.string   :foreign_key_name, null: false
      t.integer  :foreign_key_id
    end
    add_index :version_associations, [:version_id]
    add_index :version_associations,
      [:foreign_key_name, :foreign_key_id],
      name: "index_version_associations_on_foreign_key"
  end

  def self.down
    remove_index :version_associations, [:version_id]
    remove_index :version_associations,
      name: "index_version_associations_on_foreign_key"
    drop_table :version_associations
  end
end