Deadlock happens when sink to mysql

Posted by 徐涛 on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Deadlock-happens-when-sink-to-mysql-tp24596.html

Hi Experts,

I use the following sql, and sink to mysql, 

    select

    album_id, date

    count(1)

from

    coupon_5_discount_date_conv

group by

    album_id, date;

when sink to mysql, the following SQL is executed: insert into xxx (c1,c2,c3) values (?,?,?) on duplicate key update c1=VALUES(c1),c2=VALUES(c2), c3=VALUES(c3)

        The engine is InnoDB, column c1,c2 is unique key, the isolation level is READ COMMITTED. But in the log a deadlock exception happens.

As I know, because the unique key exists, only the line lock will be applied, no gap lock will be applied. And due to a group by sentence, the same unique key should be written by the same thread. So in this case, why the dead lock should happened? Could anyone help me? Thanks a lot.

Best

Henry