When you perform an upsert operation on a Google BigQuery target, you must configure the upsert fields for the target table. You can use an ID field for standard objects. Ensure that you include the upsert field in the field mappings for the task.
Rules and Guidelines
Consider the following rules and guidelines when you perform an upsert operation on a Google BigQuery target:
•You cannot use streaming mode to write data to a Google BigQuery target.
•When you configure a Google BigQuery connection to use simple or hybrid connection mode, you cannot configure upsert operations for columns of the Record data type and repeated columns.
•When you configure a Google BigQuery connection to use complex connection mode, you cannot configure an upsert operation.