public function clearCache()
    {
        $dbInstace = $this->getDbInstance();
        $sql = '
            DELETE FROM `cache`;
            VACUUM;
        ';
        $stmt = $dbInstace->prepare($sql);
        if ($stmt->execute()) {
            return;
        } else {
            $error = $stmt->errorInfo();
            $errorMsg = $error[2];
            throw new \RuntimeException('SQLite Exception: ' . $errorMsg . ' in SQL: <br /><pre>' . $sql . '</pre>');
        }
    }