gistfile1.rb

# A migration that will continue to work after refactoring
class FutureProofMigration < ActiveRecord::Migration
  # Redefine models used in the migration as empty inner classes.  This removes all validations and magic.
  class Model < ActiveRecord::Base; end

  # Either don't rely on associations or declare them as referring to the new inner class
  class DependentModel < ActiveRecord::Base
    belongs_to :model, :class_name => "FutureProofMigration::Model"
  end

  def up
    # Can safely use model class to perform transformations without dropping to sql.  Model class may be removed or refactored without breaking this migration
    Model.update_all ... blah blah...
  end
end