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vendor/yiisoft/yii2/caching/DbDependency.php

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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;
+    }
+}