Method _set_polymorphic_identity

lib/sqlalchemy/orm/mapper.py:1906–1928

(state)

        if setter:

            def _set_polymorphic_identity(state):
                dict_ = state.dict
                # TODO: what happens if polymorphic_on column attribute name
                # does not match .key?

                polymorphic_identity = (
                    state.manager.mapper.polymorphic_identity
                )
                if (
                    polymorphic_identity is None
                    and state.manager.mapper.polymorphic_abstract
                ):
                    raise sa_exc.InvalidRequestError(
                        f"Can't instantiate class for {state.manager.mapper}; "
                        "mapper is marked polymorphic_abstract=True"
                    )

                state.get_impl(polymorphic_key).set(
                    state,
                    dict_,
                    polymorphic_identity,
                    None,
                )

            self._polymorphic_attr_key = polymorphic_key