title: Yii Model with composite primary key
body: <p>My MySQL table's primary is a composite of 2 columns: space_id (INTEGER) and day (DATE).</p>
  
  <pre><code>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;
  </code></pre>
  
  <p>It works fine in raw SQL, it complains if I try to create a duplicate, but lets me create rows the the same day or the same space_id.</p>
  
  <p>However, in Yii when using new Object() and save(), it complains as if "space_id" has to be unique.</p>
  
  <p>I used "Giix" to generate the model if it matters.</p>
  
  <p>I tried to add this code to the model, but it didn't help:</p>
  
  <pre><code>public function primaryKey(){
              return array('space_id', 'day');
          }
  </code></pre>