The field mapping page displays key icons for primary key fields. Other Amazon Redshift key types are not marked. You must map a non-key field for update operation. If you use Amazon Redshift Identity fields in field mappings, map all available Identity fields or none. The Identity fields contain data that is automatically generated by Amazon Redshift.
You cannot map identity columns in a field map, if the identity column is not part of a key. If an identity column is part of a key, you must map the identity column in field map. However, you cannot set a value on the identity column from source.