JDBC sink connector - Upsert on non-primary key field

Hi, I am using JDBC sink connector to push data from kafka topic to mysql table.

Table has been created with pkey column auto increment primary key. Primary key is not coming from topic but it is created in database table but I want to upsert table on one of the unique columns which is not primary key. Kindly help me how can I configure that?

I tried using upsert with pk.mode=record_value and in pk.fields=my_unique_field but it is just inserting records not updating.

Kindly help.