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<?php
/**
* @link http://www.yiiframework.com/
* @copyright Copyright (c) 2008 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
namespace yii\caching;
use Yii;
use yii\base\InvalidConfigException;
use yii\db\Connection;
use yii\di\Instance;
/**
* DbDependency represents a dependency based on the query result of a SQL statement.
*
* If the query result changes, the dependency is considered as changed.
* The query is specified via the [[sql]] property.
*
* For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @since 2.0
*/
class DbDependency extends Dependency
{
/**
* @var string the application component ID of the DB connection.
*/
public $db = 'db';
/**
* @var string the SQL query whose result is used to determine if the dependency has been changed.
* Only the first row of the query result will be used.
*/
public $sql;
/**
* @var array the parameters (name => value) to be bound to the SQL statement specified by [[sql]].
*/
public $params = [];
/**
* Generates the data needed to determine if dependency has been changed.
* This method returns the value of the global state.
* @param CacheInterface $cache the cache component that is currently evaluating this dependency
* @return mixed the data needed to determine if dependency has been changed.
* @throws InvalidConfigException if [[db]] is not a valid application component ID
*/
protected function generateDependencyData($cache)
{
/* @var $db Connection */
$db = Instance::ensure($this->db, Connection::className());
if ($this->sql === null) {
throw new InvalidConfigException('DbDependency::sql must be set.');
}
if ($db->enableQueryCache) {
// temporarily disable and re-enable query caching
$db->enableQueryCache = false;
$result = $db->createCommand($this->sql, $this->params)->queryOne();
$db->enableQueryCache = true;
} else {
$result = $db->createCommand($this->sql, $this->params)->queryOne();
}
return $result;
}
}
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