def update(attribute_names = @attributes.keys)
      attributes_with_values = arel_attributes_values(false, false, attribute_names)
      return 0 if attributes_with_values.empty?
      klass = self.class
      stmt = klass.unscoped.where(klass.arel_table[klass.primary_key].eq(id)).arel.compile_update(attributes_with_values)
      klass.connection.update stmt
    end
def update(attribute_names = @attributes.keys)
      attributes_with_values = arel_attributes_values(false, false, attribute_names)
      return 0 if attributes_with_values.empty?
      klass = self.class
      stmt = klass.unscoped.where(klass.arel_table[klass.primary_key].eq(id)).arel.compile_update(attributes_with_values)
      klass.connection.update stmt
    end
Updates the associated record with values matching those of the instance attributes.
 Returns the number of affected rows.