Function identity_key

lib/sqlalchemy/orm/util.py:410–490

r"""Generate "identity key" tuples, as are used as keys in the :attr:`.Session.identity_map` dictionary. This function has several call styles: * ``identity_key(class, ident, identity_token=token)`` This form receives a mapped class and a primary key scalar or tuple as an

(
    class_: Optional[Type[_T]] = None,
    ident: Union[Any, Tuple[Any, ...]] = None,
    *,
    instance: Optional[_T] = None,
    row: Optional[Union[Row[Unpack[TupleAny]], RowMapping]] = None,
    identity_token: Optional[Any] = None,
)

def identity_key(
    class_: Optional[Type[_T]] = None,
    ident: Union[Any, Tuple[Any, ...]] = None,
    *,
    instance: Optional[_T] = None,
    row: Optional[Union[Row[Unpack[TupleAny]], RowMapping]] = None,
    identity_token: Optional[Any] = None,
) -> _IdentityKeyType[_T]:
    r"""Generate "identity key" tuples, as are used as keys in the
    :attr:`.Session.identity_map` dictionary.

    This function has several call styles:

    * ``identity_key(class, ident, identity_token=token)``

      This form receives a mapped class and a primary key scalar or
      tuple as an argument.

      E.g.::

        >>> identity_key(MyClass, (1, 2))
        (<class '__main__.MyClass'>, (1, 2), None)

      :param class: mapped class (must be a positional argument)
      :param ident: primary key, may be a scalar or tuple argument.
      :param identity_token: optional identity token

    * ``identity_key(instance=instance)``

      This form will produce the identity key for a given instance.  The
      instance need not be persistent, only that its primary key attributes
      are populated (else the key will contain ``None`` for those missing
      values).

      E.g.::

        >>> instance = MyClass(1, 2)
        >>> identity_key(instance=instance)
        (<class '__main__.MyClass'>, (1, 2), None)

      In this form, the given instance is ultimately run though
      :meth:`_orm.Mapper.identity_key_from_instance`, which will have the
      effect of performing a database check for the corresponding row
      if the object is expired.

      :param instance: object instance (must be given as a keyword arg)

    * ``identity_key(class, row=row, identity_token=token)``

      This form is similar to the class/tuple form, except is passed a
      database result row as a :class:`.Row` or :class:`.RowMapping` object.

      E.g.::

        >>> row = engine.execute(text("select * from table where a=1 and b=2")).first()
        >>> identity_key(MyClass, row=row)
        (<class '__main__.MyClass'>, (1, 2), None)