Disordering events in a transaction with TiCDC may cause conflicts in downstream execution

[nongfushanquan]

What did you do?

create table cptesttable (k INT NOT NULL PRIMARY KEY, v INT NOT NULL, UNIQUE(v));
MySQL [cptestdb]> BEGIN;
MySQL [cptestdb]> INSERT INTO cptesttable VALUES (1, 1);
MySQL [cptestdb]> INSERT INTO cptesttable VALUES (2, 2);
MySQL [cptestdb]> COMMIT;
MySQL [cptestdb]> BEGIN;
MySQL [cptestdb]> UPDATE cptesttable SET v = 3 WHERE k = 2;
MySQL [cptestdb]> UPDATE cptesttable SET v = 2 WHERE k = 1;
MySQL [cptestdb]> COMMIT;

What did you expect to see?

MySQL [cptestdb]> UPDATE cptesttable SET v = 3 WHERE k = 2;
MySQL [cptestdb]> UPDATE cptesttable SET v = 2 WHERE k = 1;

What did you see instead?

MySQL [cptestdb]> UPDATE cptesttable SET v = 2 WHERE k = 1;
MySQL [cptestdb]> UPDATE cptesttable SET v = 3 WHERE k = 2;

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

(paste TiDB cluster version here)

Upstream TiKV version (execute tikv-server --version):

(paste TiKV version here)

TiCDC version (execute cdc version):
6.5 & 7.1

(paste TiCDC version here)

[nongfushanquan]

/assign @sdojjy