Method expire

lib/sqlalchemy/orm/session.py:3333–3376

Expire the attributes on an instance. Marks the attributes of an instance as out of date. When an expired attribute is next accessed, a query will be issued to the :class:`.Session` object's current transactional context in order to load all expired attributes for th

(
        self, instance: object, attribute_names: Optional[Iterable[str]] = None
    )

            state._expire(state.dict, self.identity_map._modified)

    def expire(
        self, instance: object, attribute_names: Optional[Iterable[str]] = None
    ) -> None:
        """Expire the attributes on an instance.

        Marks the attributes of an instance as out of date. When an expired
        attribute is next accessed, a query will be issued to the
        :class:`.Session` object's current transactional context in order to
        load all expired attributes for the given instance.   Note that
        a highly isolated transaction will return the same values as were
        previously read in that same transaction, regardless of changes
        in database state outside of that transaction.

        To expire all objects in the :class:`.Session` simultaneously,
        use :meth:`Session.expire_all`.

        The :class:`.Session` object's default behavior is to
        expire all state whenever the :meth:`Session.rollback`
        or :meth:`Session.commit` methods are called, so that new
        state can be loaded for the new transaction.   For this reason,
        calling :meth:`Session.expire` only makes sense for the specific
        case that a non-ORM SQL statement was emitted in the current
        transaction.

        :param instance: The instance to be refreshed.
        :param attribute_names: optional list of string attribute names
          indicating a subset of attributes to be expired.

        .. seealso::

            :ref:`session_expire` - introductory material

            :meth:`.Session.expire`

            :meth:`.Session.refresh`

            :meth:`_orm.Query.populate_existing`

        """
        try:
            state = attributes.instance_state(instance)
        except exc.NO_STATE as err:
            raise exc.UnmappedInstanceError(instance) from err
        self._expire_state(state, attribute_names)

    def _expire_state(
        self,