how to handle additional increment column in target database with goldengate?

In my situation, I'm doing a initialization in MySQL by moving data from oracle table. there is no auto increment column in oracle table, but the MySQL table has such column, say id column. ideally, the id column will not appear in the funcition colmap in replicat configuration. Unfortunately, I got the below error:
Error with default mapping. No matching fields found in source and target
The following target columns were not mapped:
id

is there any solution for this? I think the mysql column auto increment column can work well, during the initialization, we only do inserting by employing the extract and replicat.