Module « sqlalchemy.orm »

Fonction with_expression - module sqlalchemy.orm

Signature de la fonction with_expression

def with_expression(key, expression) 

Description

with_expression.__doc__

Apply an ad-hoc SQL expression to a "deferred expression" attribute.

    This option is used in conjunction with the :func:`_orm.query_expression`
    mapper-level construct that indicates an attribute which should be the
    target of an ad-hoc SQL expression.

    E.g.::


        sess.query(SomeClass).options(
            with_expression(SomeClass.x_y_expr, SomeClass.x + SomeClass.y)
        )

    .. versionadded:: 1.2

    :param key: Attribute to be undeferred.

    :param expr: SQL expression to be applied to the attribute.

    .. note:: the target attribute is populated only if the target object
       is **not currently loaded** in the current :class:`_orm.Session`
       unless the :meth:`_query.Query.populate_existing` method is used.
       Please refer to :ref:`mapper_querytime_expression` for complete
       usage details.

    .. seealso::

        :ref:`mapper_querytime_expression`