yii2

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