module ActiveRecord::Locking::Optimistic

def update_record(attribute_names = @attributes.keys) #:nodoc:
  return super unless locking_enabled?
  return 0 if attribute_names.empty?
  lock_col = self.class.locking_column
  previous_lock_value = send(lock_col).to_i
  increment_lock
  attribute_names += [lock_col]
  attribute_names.uniq!
  begin
    relation = self.class.unscoped
    stmt = relation.where(
      relation.table[self.class.primary_key].eq(id).and(
        relation.table[lock_col].eq(self.class.quote_value(previous_lock_value, column_for_attribute(lock_col)))
      )
    ).arel.compile_update(arel_attributes_with_values_for_update(attribute_names))
    affected_rows = self.class.connection.update stmt
    unless affected_rows == 1
      raise ActiveRecord::StaleObjectError.new(self, "update")
    end
    affected_rows
  # If something went wrong, revert the version.
  rescue Exception
    send(lock_col + '=', previous_lock_value)
    raise
  end
end