/**
     * 连接数据库
     * @access public
     * @return PDO
     * @throws \Exception
     */
    public function connect() {
        if (!$this->pdo) {
            try {
                $this->pdo = new PDO($this->dsn, $this->username, $this->password, $this->params);
            } catch (\PDOException $e) {
                throw $e;
            }
        }
        return $this->pdo;
    }


    /**
     * 执行查询 返回数据集
     *
     * @param string $sql
     * @param array  $bind
     * @param bool   $cache
     *
     * @return array
     * @throws \Exception
     */
    public function query($sql, $bind = [], $cache = false) {
        $items = null;
        $dbCache = null;
        if ($cache) {
            /* @var $dbCache DBCache */
            $dbCache = Ioc::get(DBCache::class);
            $items = $dbCache->queryCache($sql, $bind);
        }
        if (!$items) {
            $items = [];
            $this->execute($sql, $bind, false);
            $procedure = in_array(strtolower(substr(trim($sql), 0, 4)), ['call', 'exec']);

    
PDO->__construct(...)
rap\db\Connection->connect(...)
rap\db\Connection->execute(...)
rap\db\Connection->query(...)
rap\db\Select->findAll(...)
rap\db\Select->find(...)
rap\db\Record::find(...)
cloud\SiteConfig->handler(...)
rap\web\Application->start(...)
require(...)