Yii INSERT ... 重复更新

I am working on a Yii project. How can I use the ON DUPLICATE feature of MySQL ( http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html ) when doing a save() on a Yii model?

我的MySQL如下:

CREATE TABLE `ck_space_calendar_cache` (
  `space_id` int(11) NOT NULL,
  `day` date NOT NULL,
  `available` tinyint(1) unsigned NOT NULL DEFAULT '0',
  `price` decimal(12,2) DEFAULT NULL,
  `offer` varchar(45) DEFAULT NULL,
  `presale_date` date DEFAULT NULL,
  `presale_price` decimal(12,2) DEFAULT NULL,
  `value_x` int(11) DEFAULT NULL,
  `value_y` int(11) DEFAULT NULL,
  PRIMARY KEY (`space_id`,`day`),
  KEY `space` (`space_id`),
  CONSTRAINT `space` FOREIGN KEY (`space_id`) REFERENCES `ck_space` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

我的PHP如下:

$cache = new SpaceCalendarCache();
$cache->attributes = $day; //Some array with attributes              
$cache->save();

如果我的主键 (sapce_id,day) 中存在重复项，我不希望它抱怨，我只希望它使用最新数据进行更新.