lastStatement property

If set to true, this statement marks the end of the transaction.

After this statement executes, you must commit or abort the transaction. Attempts to execute any other requests against this transaction (including reads and queries) are rejected. For DML statements, setting this option might cause some error reporting to be deferred until commit time (for example, validation of unique constraints). Given this, successful execution of a DML statement shouldn't be assumed until a subsequent Commit call completes successfully.

Optional.