Method with_expression

lib/sqlalchemy/orm/strategy_options.py:722–757

r"""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.

(
        self,
        key: _AttrType,
        expression: _ColumnExpressionArgument[Any],
    )

        )

    def with_expression(
        self,
        key: _AttrType,
        expression: _ColumnExpressionArgument[Any],
    ) -> Self:
        r"""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.::

            stmt = select(SomeClass).options(
                with_expression(SomeClass.x_y_expr, SomeClass.x + SomeClass.y)
            )

        :param key: Attribute to be populated

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

        .. seealso::

            :ref:`orm_queryguide_with_expression` - background and usage
            examples

        """

        expression = _orm_full_deannotate(
            coercions.expect(roles.LabeledColumnExprRole, expression)
        )

        return self._set_column_strategy(
            (key,), {"query_expression": True}, extra_criteria=(expression,)
        )

    def selectin_polymorphic(self, classes: Iterable[Type[Any]]) -> Self:
        """Indicate an eager load should take place for all attributes