你好，这是我的部分代码：

db = pymysql.connect(
    host = ....., 
    user = ....., 
    passwd = ....., 
    db = ....., 
    port = ....., 
    connect_timeout = 5 , 
    use_unicode = True, 
    charset = "utf8",
    autocommit = True,
)

c = db.cursor(pymysql.cursors.SSDictCursor)
data  = c.execute(my_query) # for example SELECT * FROM PEOPLE
run = True
while run:
    ### processing in batches of 50
    batch = []
    for i in range(50):
        row = data.fetchone()
        if not row:
             run = False 
             break 
        row = do_something(row)
        batch += [row]

    do_stuff_that takes_3_minutes(batch)

我的问题是，大约一个小时后，这个代码就会被卡住 data.fetchone() ，但它没有退出或显示任何错误，只是被卡住了。我知道这是因为，我在每条指令之前和之后都添加了print语句，最后一次输出到控制台的是之前的print语句 fetchone()