* Returns the list of object properties that are included as-is in the
* cache, only when they're not too big, and are lazily loaded by self::loadExtraFromDB().
* @param string $prefix Must be the empty string
* Returns the list of object properties that are included as-is in the
* cache, only when they're not too big, and are lazily loaded by self::loadExtraFromDB().
* @param string $prefix Must be the empty string