YII 类库手册

protected function addValue($key,$value,$expire)
{
    if(!$this->_gced && mt_rand(0,1000000)<$this->_gcProbability)
    {
        $this->gc();
        $this->_gced=true;
    }

    if($expire>0)
        $expire+=time();
    else
        $expire=0;
    $sql="INSERT INTO {$this->cacheTableName} (id,expire,value) VALUES ('$key',$expire,:value)";
    try
    {
        $command=$this->getDbConnection()->createCommand($sql);
        $command->bindValue(':value',$value,PDO::PARAM_LOB);
        $command->execute();
        return true;
    }
    catch(Exception $e)
    {
        return false;
    }
}

protected function createCacheTable($db,$tableName)
{
    $driver=$db->getDriverName();
    if($driver==='mysql')
        $blob='LONGBLOB';
    else if($driver==='pgsql')
        $blob='BYTEA';
    else
        $blob='BLOB';
    $sql=<<<EOD
CREATE TABLE $tableName
(
id CHAR(128) PRIMARY KEY,
expire INTEGER,
value $blob
)
EOD;
    $db->createCommand($sql)->execute();
}

protected function deleteValue($key)
{
    $sql="DELETE FROM {$this->cacheTableName} WHERE id='$key'";
    $this->getDbConnection()->createCommand($sql)->execute();
    return true;
}

protected function flushValues()
{
    $this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName}")->execute();
    return true;
}

protected function gc()
{
    $this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time())->execute();
}

public function getDbConnection()
{
    if($this->_db!==null)
        return $this->_db;
    else if(($id=$this->connectionID)!==null)
    {
        if(($this->_db=Yii::app()->getComponent($id)) instanceof CDbConnection)
            return $this->_db;
        else
            throw new CException(Yii::t('yii','CDbCache.connectionID "{id}" is invalid. Please make sure it refers to the ID of a CDbConnection application component.',
                array('{id}'=>$id)));
    }
    else
    {
        $dbFile=Yii::app()->getRuntimePath().DIRECTORY_SEPARATOR.'cache-'.Yii::getVersion().'.db';
        return $this->_db=new CDbConnection('sqlite:'.$dbFile);
    }
}

public function getGCProbability()
{
    return $this->_gcProbability;
}

protected function getValue($key)
{
    $time=time();
    $sql="SELECT value FROM {$this->cacheTableName} WHERE id='$key' AND (expire=0 OR expire>$time)";
    $db=$this->getDbConnection();
    if($db->queryCachingDuration>0)
    {
        $duration=$db->queryCachingDuration;
        $db->queryCachingDuration=0;
        $result=$db->createCommand($sql)->queryScalar();
        $db->queryCachingDuration=$duration;
        return $result;
    }
    else
        return $db->createCommand($sql)->queryScalar();
}

protected function getValues($keys)
{
    if(empty($keys))
        return array();

    $ids=implode("','",$keys);
    $time=time();
    $sql="SELECT id, value FROM {$this->cacheTableName} WHERE id IN ('$ids') AND (expire=0 OR expire>$time)";

    $db=$this->getDbConnection();
    if($db->queryCachingDuration>0)
    {
        $duration=$db->queryCachingDuration;
        $db->queryCachingDuration=0;
        $rows=$db->createCommand($sql)->queryAll();
        $db->queryCachingDuration=$duration;
    }
    else
        $rows=$db->createCommand($sql)->queryAll();

    $results=array();
    foreach($keys as $key)
        $results[$key]=false;
    foreach($rows as $row)
        $results[$row['id']]=$results[$row['value']];
    return $results;
}

public function init()
{
    parent::init();

    $db=$this->getDbConnection();
    $db->setActive(true);
    if($this->autoCreateCacheTable)
    {
        $sql="DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time();
        try
        {
            $db->createCommand($sql)->execute();
        }
        catch(Exception $e)
        {
            $this->createCacheTable($db,$this->cacheTableName);
        }
    }
}

public function setDbConnection($value)
{
    $this->_db=$value;
}

public function setGCProbability($value)
{
    $value=(int)$value;
    if($value<0)
        $value=0;
    if($value>1000000)
        $value=1000000;
    $this->_gcProbability=$value;
}

protected function setValue($key,$value,$expire)
{
    $this->deleteValue($key);
    return $this->addValue($key,$value,$expire);
}