The list of relations to be locked during the transaction.
    In general, include all the relations your transaction will
    access. If you specify the AUTO LOCKING clause, constraints and
    triggers defined on the reserved relations will be able to access
    additional relations that do not appear in the list of reserved
    relations.

    Note that if you use the RESERVING clause without the AUTO
    LOCKING clause, you can access only those relations that you
    have explicitly reserved.