Method load_only

lib/sqlalchemy/orm/strategy_options.py:164–237

r"""Indicate that for a particular entity, only the given list of column-based attribute names should be loaded; all others will be deferred. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation.

(self, *attrs: _AttrType, raiseload: bool = False)

        return cloned

    def load_only(self, *attrs: _AttrType, raiseload: bool = False) -> Self:
        r"""Indicate that for a particular entity, only the given list
        of column-based attribute names should be loaded; all others will be
        deferred.

        This function is part of the :class:`_orm.Load` interface and supports
        both method-chained and standalone operation.

        Example - given a class ``User``, load only the ``name`` and
        ``fullname`` attributes::

            session.query(User).options(load_only(User.name, User.fullname))

        Example - given a relationship ``User.addresses -> Address``, specify
        subquery loading for the ``User.addresses`` collection, but on each
        ``Address`` object load only the ``email_address`` attribute::

            session.query(User).options(
                subqueryload(User.addresses).load_only(Address.email_address)
            )

        For a statement that has multiple entities,
        the lead entity can be
        specifically referred to using the :class:`_orm.Load` constructor::

            stmt = (
                select(User, Address)
                .join(User.addresses)
                .options(
                    Load(User).load_only(User.name, User.fullname),
                    Load(Address).load_only(Address.email_address),
                )
            )

        When used together with the
        :ref:`populate_existing <orm_queryguide_populate_existing>`
        execution option only the attributes listed will be refreshed.

        :param \*attrs: Attributes to be loaded, all others will be deferred.

        :param raiseload: raise :class:`.InvalidRequestError` rather than
         lazy loading a value when a deferred attribute is accessed. Used
         to prevent unwanted SQL from being emitted.

         .. versionadded:: 2.0

        .. seealso::

            :ref:`orm_queryguide_column_deferral` - in the
            :ref:`queryguide_toplevel`

        :param \*attrs: Attributes to be loaded, all others will be deferred.

        :param raiseload: raise :class:`.InvalidRequestError` rather than
         lazy loading a value when a deferred attribute is accessed. Used
         to prevent unwanted SQL from being emitted.

         .. versionadded:: 2.0