Classe « Session »

Méthode sqlalchemy.orm.Session.enable_relationship_loading

Signature de la méthode enable_relationship_loading

def enable_relationship_loading(self, obj) 

Description

enable_relationship_loading.__doc__

Associate an object with this :class:`.Session` for related
        object loading.

        .. warning::

            :meth:`.enable_relationship_loading` exists to serve special
            use cases and is not recommended for general use.

        Accesses of attributes mapped with :func:`_orm.relationship`
        will attempt to load a value from the database using this
        :class:`.Session` as the source of connectivity.  The values
        will be loaded based on foreign key and primary key values
        present on this object - if not present, then those relationships
        will be unavailable.

        The object will be attached to this session, but will
        **not** participate in any persistence operations; its state
        for almost all purposes will remain either "transient" or
        "detached", except for the case of relationship loading.

        Also note that backrefs will often not work as expected.
        Altering a relationship-bound attribute on the target object
        may not fire off a backref event, if the effective value
        is what was already loaded from a foreign-key-holding value.

        The :meth:`.Session.enable_relationship_loading` method is
        similar to the ``load_on_pending`` flag on :func:`_orm.relationship`.
        Unlike that flag, :meth:`.Session.enable_relationship_loading` allows
        an object to remain transient while still being able to load
        related items.

        To make a transient object associated with a :class:`.Session`
        via :meth:`.Session.enable_relationship_loading` pending, add
        it to the :class:`.Session` using :meth:`.Session.add` normally.
        If the object instead represents an existing identity in the database,
        it should be merged using :meth:`.Session.merge`.

        :meth:`.Session.enable_relationship_loading` does not improve
        behavior when the ORM is used normally - object references should be
        constructed at the object level, not at the foreign key level, so
        that they are present in an ordinary way before flush()
        proceeds.  This method is not intended for general use.

        .. seealso::

            :paramref:`_orm.relationship.load_on_pending` - this flag
            allows per-relationship loading of many-to-ones on items that
            are pending.

            :func:`.make_transient_to_detached` - allows for an object to
            be added to a :class:`.Session` without SQL emitted, which then
            will unexpire attributes on access.