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Classe « Session »

Méthode sqlalchemy.orm.Session.enable_relationship_loading

Signature de la méthode enable_relationship_loading

def enable_relationship_loading(self, obj: 'object') -> 'None' 

Description

help(Session.enable_relationship_loading)

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.

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