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113 lines
3.2 KiB
113 lines
3.2 KiB
14 years ago
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<?php
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/**
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* CDbCacheDependency 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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* CDbCacheDependency represents a dependency based on the query result of a SQL statement.
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*
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* If the query result (a scalar) changes, the dependency is considered as changed.
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* To specify the SQL statement, set {@link sql} property.
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* The {@link connectionID} property specifies the ID of a {@link CDbConnection} application
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* component. It is this DB connection that is used to perform the query.
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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.dependencies
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* @since 1.0
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*/
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class CDbCacheDependency extends CCacheDependency
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{
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/**
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* @var string the ID of a {@link CDbConnection} application component. Defaults to 'db'.
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*/
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public $connectionID='db';
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/**
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* @var string the SQL statement whose result is used to determine if the dependency has been changed.
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* Note, the SQL statement should return back a single value.
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*/
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public $sql;
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/**
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* @var array parameters (name=>value) to be bound to the SQL statement specified by {@link sql}.
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* @since 1.1.4
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*/
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public $params;
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private $_db;
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/**
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* Constructor.
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* @param string $sql the SQL statement whose result is used to determine if the dependency has been changed.
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*/
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public function __construct($sql=null)
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{
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$this->sql=$sql;
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}
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/**
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* PHP sleep magic method.
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* This method ensures that the database instance is set null because it contains resource handles.
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* @return array
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*/
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public function __sleep()
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{
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$this->_db=null;
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return array_keys((array)$this);
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}
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/**
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* Generates the data needed to determine if dependency has been changed.
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* This method returns the value of the global state.
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* @return mixed the data needed to determine if dependency has been changed.
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*/
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protected function generateDependentData()
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{
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if($this->sql!==null)
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{
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$db=$this->getDbConnection();
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$command=$db->createCommand($this->sql);
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if(is_array($this->params))
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{
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foreach($this->params as $name=>$value)
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$command->bindValue($name,$value);
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}
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if($db->queryCachingDuration>0)
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{
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// temporarily disable and re-enable query caching
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$duration=$db->queryCachingDuration;
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$db->queryCachingDuration=0;
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$result=$command->queryRow();
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$db->queryCachingDuration=$duration;
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}
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else
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$result=$command->queryRow();
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return $result;
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}
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else
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throw new CException(Yii::t('yii','CDbCacheDependency.sql cannot be empty.'));
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}
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/**
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* @return CDbConnection the DB connection instance
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* @throws CException if {@link connectionID} does not point to a valid application component.
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*/
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protected function getDbConnection()
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{
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if($this->_db!==null)
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return $this->_db;
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else
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{
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if(($this->_db=Yii::app()->getComponent($this->connectionID)) instanceof CDbConnection)
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return $this->_db;
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else
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throw new CException(Yii::t('yii','CDbCacheDependency.connectionID "{id}" is invalid. Please make sure it refers to the ID of a CDbConnection application component.',
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array('{id}'=>$this->connectionID)));
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}
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}
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}
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