Flink这种一般会是什么情况引起的呢？

Flink这种一般会是什么情况引起的呢？我 3秒 的窗口计算总和，但是在现场有溢些 group by 的分组无法计算出值。数据也是有在发送的。WATERMARK 也是设置了允许延迟 30s。

CREATE VIEW IF NOT EXISTS v_company_link_window_3s AS
SELECT window_start,
window_end,
company_id,
link_id,
SUM(send_bytes) AS flow_in,
SUM(recv_bytes) AS flow_out
FROM TABLE(
TUMBLE(TABLE v_company_link, DESCRIPTOR(data_time), INTERVAL '3' SECONDS)) AS tmp
GROUP BY window_start,
window_end,
company_id,
link_id
;