Module « sqlalchemy.orm »

Fonction defer - module sqlalchemy.orm

Signature de la fonction defer

def defer(key, *addl_attrs, **kw) 

Description

defer.__doc__

Indicate that the given column-oriented attribute should be deferred,
    e.g. not loaded until accessed.

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

    e.g.::

        from sqlalchemy.orm import defer

        session.query(MyClass).options(
                            defer("attribute_one"),
                            defer("attribute_two"))

        session.query(MyClass).options(
                            defer(MyClass.attribute_one),
                            defer(MyClass.attribute_two))

    To specify a deferred load of an attribute on a related class,
    the path can be specified one token at a time, specifying the loading
    style for each link along the chain.  To leave the loading style
    for a link unchanged, use :func:`_orm.defaultload`::

        session.query(MyClass).options(defaultload("someattr").defer("some_column"))

    A :class:`_orm.Load` object that is present on a certain path can have
    :meth:`_orm.Load.defer` called multiple times,
    each will operate on the same
    parent entity::


        session.query(MyClass).options(
                        defaultload("someattr").
                            defer("some_column").
                            defer("some_other_column").
                            defer("another_column")
            )

    :param key: Attribute to be deferred.

    :param raiseload: raise :class:`.InvalidRequestError` if the column
     value is to be loaded from emitting SQL.   Used to prevent unwanted
     SQL from being emitted.

     .. versionadded:: 1.4

     .. seealso::

        :ref:`deferred_raiseload`

    :param \*addl_attrs: This option supports the old 0.8 style
     of specifying a path as a series of attributes, which is now superseded
     by the method-chained style.

        .. deprecated:: 0.9  The \*addl_attrs on :func:`_orm.defer` is
           deprecated and will be removed in a future release.   Please
           use method chaining in conjunction with defaultload() to
           indicate a path.


    .. seealso::

        :ref:`deferred`

        :func:`_orm.undefer`