thinkphp5 模型多次save操作，会产生重复的主键ID

在thinkphp5.0.7版本下使用，如果用模型多次执行save操作，会提示产生的主键ID重复。代码如下

 $FbPostImageModel = new FbPostImage();
 for ($i=0; $i < 10; $i++) { 
      $data["object_id"] = rand(0, 10000);
     $data["picture"] = "test";
     $data["images"] = "test";
     $data["link"] = "abc";
     $data["caption"] = "";
     $FbPostImageModel->isUpdate(false)->save($data);
 }

异常提示：

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry "17" for key "PRIMARY"
            // 调试结束
            $this->debug(false);

            $this->numRows = $this->PDOStatement->rowCount();
            return $this->numRows;
        } catch (PDOException $e) {
            if ($this->config["break_reconnect"] && $this->isBreak($e)) {
                return $this->close()->execute($sql, $bind);
            }
            throw new PDOException($e, $this->config, $this->getLastsql());
        }
    }

    /**
     * 根据参数绑定组装最终的SQL语句 便于调试
     * @access public
     * @param string    $sql 带参数绑定的sql语句
     * @param array     $bind 参数绑定列表
     * @return string
Call Stack
in Connection.php line 457
at Connection->execute("INSERT INTO `fb_post...", ["__data__object_id" => [731, 2], "__data__picture" => ["test", 2], "__data__images" => [""test"", 2], ...]) in Query.php line 239
at Query->execute("INSERT INTO `fb_post...", ["__data__object_id" => [731, 2], "__data__picture" => ["test", 2], "__data__images" => [""test"", 2], ...]) in Query.php line 2062
at Query->insert(["object_id" => 731, "picture" => "test", "images" => ""test"", ...]) in Model.php line 934
at Model->save(["object_id" => 731, "picture" => "test", "images" => "test", ...]) in Index.php line 40
at Index->testMultiInsert()
at ReflectionMethod->invokeArgs(object(Index), []) in App.php line 224
at App::invokeMethod([object(Index), "testmultiinsert"], []) in App.php line 389
at App::module(["Index", "index", "testMultiInsert"], ["app_namespace" => "app", "app_debug" => true, "app_trace" => false, ...], null) in App.php line 130
at App::run() in start.php line 18
at require("/home/web/facebook_p...") in index.php line 20

生成的sql是：

INSERT INTO `fb_post_image` (`object_id` , `picture` , `images` , `link` , `caption` , `update_time`) VALUES ("8822" , "test" , ""test"" , "abc" , "" , "2017-03-09 14:47:40")

这里的17是自增主键ID。为了避免这个问题，需要将新增代码改成

 $FbPostImageModel->isUpdate(false)->data($data, true)->save();

生成的sql是

INSERT INTO `fb_post_image` (`object_id` , `picture` , `images` , `link` , `caption` , `update_time`) VALUES ("7774" , "test" , ""test"" , "abc" , "" , "2017-03-09 14:48:49")

这可能是thinkphp的bug。