When you specify the pre-SQL, post-SQL, and SQL query commands in the source and target properties for Google BigQuery and upgrade the connection to Google BigQuery V2, ensure that the number of characters in the queries in the Google BigQuery ODBC connection or Google BigQuery V1 connection must not exceed 65535. Otherwise, the queries are truncated.

Even after you replace the connection with the Google BigQuery V2 connection, the object field displays the object that you selected in the earlier connection. You need to re-import the Google BigQuery object and remap the fields in the mapping.