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Qiang Xue
314
framework/caching/DbCache.php
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314
framework/caching/DbCache.php
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<?php
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/**
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* CDbCache class file
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*
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* @author Qiang Xue <qiang.xue@gmail.com>
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* @link http://www.yiiframework.com/
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* @copyright Copyright © 2008-2011 Yii Software LLC
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* @license http://www.yiiframework.com/license/
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*/
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/**
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* CDbCache implements a cache application component by storing cached data in a database.
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*
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* CDbCache stores cache data in a DB table named {@link cacheTableName}.
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* If the table does not exist, it will be automatically created.
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* By setting {@link autoCreateCacheTable} to false, you can also manually create the DB table.
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*
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* CDbCache relies on {@link http://www.php.net/manual/en/ref.pdo.php PDO} to access database.
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* By default, it will use a SQLite3 database under the application runtime directory.
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* You can also specify {@link connectionID} so that it makes use of
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* a DB application component to access database.
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*
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* See {@link CCache} manual for common cache operations that are supported by CDbCache.
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*
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* @property integer $gCProbability The probability (parts per million) that garbage collection (GC) should be performed
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* when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
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* @property CDbConnection $dbConnection The DB connection instance.
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*
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* @author Qiang Xue <qiang.xue@gmail.com>
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* @version $Id$
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* @package system.caching
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* @since 1.0
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*/
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class CDbCache extends CCache
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{
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/**
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* @var string the ID of the {@link CDbConnection} application component. If not set,
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* a SQLite3 database will be automatically created and used. The SQLite database file
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* is <code>protected/runtime/cache-YiiVersion.db</code>.
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*/
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public $connectionID;
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/**
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* @var string name of the DB table to store cache content. Defaults to 'YiiCache'.
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* Note, if {@link autoCreateCacheTable} is false and you want to create the DB table
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* manually by yourself, you need to make sure the DB table is of the following structure:
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* <pre>
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* (id CHAR(128) PRIMARY KEY, expire INTEGER, value BLOB)
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* </pre>
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* Note, some DBMS might not support BLOB type. In this case, replace 'BLOB' with a suitable
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* binary data type (e.g. LONGBLOB in MySQL, BYTEA in PostgreSQL.)
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* @see autoCreateCacheTable
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*/
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public $cacheTableName='YiiCache';
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/**
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* @var boolean whether the cache DB table should be created automatically if it does not exist. Defaults to true.
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* If you already have the table created, it is recommended you set this property to be false to improve performance.
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* @see cacheTableName
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*/
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public $autoCreateCacheTable=true;
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/**
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* @var CDbConnection the DB connection instance
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*/
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private $_db;
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private $_gcProbability=100;
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private $_gced=false;
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/**
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* Initializes this application component.
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*
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* This method is required by the {@link IApplicationComponent} interface.
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* It ensures the existence of the cache DB table.
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* It also removes expired data items from the cache.
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*/
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public function init()
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{
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parent::init();
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$db=$this->getDbConnection();
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$db->setActive(true);
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if($this->autoCreateCacheTable)
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{
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$sql="DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time();
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try
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{
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$db->createCommand($sql)->execute();
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}
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catch(Exception $e)
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{
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$this->createCacheTable($db,$this->cacheTableName);
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}
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}
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}
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/**
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* @return integer the probability (parts per million) that garbage collection (GC) should be performed
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* when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
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*/
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public function getGCProbability()
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{
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return $this->_gcProbability;
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}
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/**
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* @param integer $value the probability (parts per million) that garbage collection (GC) should be performed
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* when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
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* This number should be between 0 and 1000000. A value 0 meaning no GC will be performed at all.
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*/
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public function setGCProbability($value)
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{
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$value=(int)$value;
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if($value<0)
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$value=0;
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if($value>1000000)
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$value=1000000;
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$this->_gcProbability=$value;
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}
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/**
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* Creates the cache DB table.
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* @param CDbConnection $db the database connection
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* @param string $tableName the name of the table to be created
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*/
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protected function createCacheTable($db,$tableName)
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{
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$driver=$db->getDriverName();
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if($driver==='mysql')
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$blob='LONGBLOB';
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else if($driver==='pgsql')
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$blob='BYTEA';
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else
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$blob='BLOB';
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$sql=<<<EOD
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CREATE TABLE $tableName
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(
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id CHAR(128) PRIMARY KEY,
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expire INTEGER,
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value $blob
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)
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EOD;
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$db->createCommand($sql)->execute();
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}
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/**
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* @return CDbConnection the DB connection instance
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* @throws CException if {@link connectionID} does not point to a valid application component.
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*/
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public function getDbConnection()
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{
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if($this->_db!==null)
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return $this->_db;
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else if(($id=$this->connectionID)!==null)
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{
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if(($this->_db=Yii::app()->getComponent($id)) instanceof CDbConnection)
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return $this->_db;
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else
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throw new CException(Yii::t('yii','CDbCache.connectionID "{id}" is invalid. Please make sure it refers to the ID of a CDbConnection application component.',
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array('{id}'=>$id)));
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}
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else
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{
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$dbFile=Yii::app()->getRuntimePath().DIRECTORY_SEPARATOR.'cache-'.Yii::getVersion().'.db';
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return $this->_db=new CDbConnection('sqlite:'.$dbFile);
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}
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}
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/**
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* Sets the DB connection used by the cache component.
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* @param CDbConnection $value the DB connection instance
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* @since 1.1.5
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*/
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public function setDbConnection($value)
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{
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$this->_db=$value;
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}
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/**
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* Retrieves a value from cache with a specified key.
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* This is the implementation of the method declared in the parent class.
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* @param string $key a unique key identifying the cached value
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* @return string the value stored in cache, false if the value is not in the cache or expired.
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*/
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protected function getValue($key)
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{
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$time=time();
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$sql="SELECT value FROM {$this->cacheTableName} WHERE id='$key' AND (expire=0 OR expire>$time)";
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$db=$this->getDbConnection();
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if($db->queryCachingDuration>0)
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{
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$duration=$db->queryCachingDuration;
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$db->queryCachingDuration=0;
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$result=$db->createCommand($sql)->queryScalar();
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$db->queryCachingDuration=$duration;
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return $result;
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}
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else
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return $db->createCommand($sql)->queryScalar();
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}
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/**
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* Retrieves multiple values from cache with the specified keys.
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* @param array $keys a list of keys identifying the cached values
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* @return array a list of cached values indexed by the keys
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*/
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protected function getValues($keys)
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{
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if(empty($keys))
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return array();
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$ids=implode("','",$keys);
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$time=time();
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$sql="SELECT id, value FROM {$this->cacheTableName} WHERE id IN ('$ids') AND (expire=0 OR expire>$time)";
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$db=$this->getDbConnection();
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if($db->queryCachingDuration>0)
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{
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$duration=$db->queryCachingDuration;
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$db->queryCachingDuration=0;
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$rows=$db->createCommand($sql)->queryAll();
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$db->queryCachingDuration=$duration;
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}
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else
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$rows=$db->createCommand($sql)->queryAll();
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$results=array();
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foreach($keys as $key)
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$results[$key]=false;
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foreach($rows as $row)
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$results[$row['id']]=$row['value'];
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return $results;
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}
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/**
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* Stores a value identified by a key in cache.
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* This is the implementation of the method declared in the parent class.
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*
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* @param string $key the key identifying the value to be cached
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* @param string $value the value to be cached
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* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
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* @return boolean true if the value is successfully stored into cache, false otherwise
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*/
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protected function setValue($key,$value,$expire)
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{
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$this->deleteValue($key);
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return $this->addValue($key,$value,$expire);
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}
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/**
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* Stores a value identified by a key into cache if the cache does not contain this key.
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* This is the implementation of the method declared in the parent class.
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*
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* @param string $key the key identifying the value to be cached
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* @param string $value the value to be cached
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* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
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* @return boolean true if the value is successfully stored into cache, false otherwise
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*/
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protected function addValue($key,$value,$expire)
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{
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if(!$this->_gced && mt_rand(0,1000000)<$this->_gcProbability)
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{
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$this->gc();
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$this->_gced=true;
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}
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if($expire>0)
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$expire+=time();
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else
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$expire=0;
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$sql="INSERT INTO {$this->cacheTableName} (id,expire,value) VALUES ('$key',$expire,:value)";
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try
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{
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$command=$this->getDbConnection()->createCommand($sql);
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$command->bindValue(':value',$value,PDO::PARAM_LOB);
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$command->execute();
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return true;
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}
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catch(Exception $e)
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{
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return false;
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}
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}
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/**
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* Deletes a value with the specified key from cache
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* This is the implementation of the method declared in the parent class.
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* @param string $key the key of the value to be deleted
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* @return boolean if no error happens during deletion
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*/
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protected function deleteValue($key)
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{
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$sql="DELETE FROM {$this->cacheTableName} WHERE id='$key'";
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$this->getDbConnection()->createCommand($sql)->execute();
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return true;
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}
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/**
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* Removes the expired data values.
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*/
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protected function gc()
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{
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$this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time())->execute();
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}
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/**
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* Deletes all values from cache.
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* This is the implementation of the method declared in the parent class.
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* @return boolean whether the flush operation was successful.
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* @since 1.1.5
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*/
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protected function flushValues()
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{
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$this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName}")->execute();
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return true;
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}
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}
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