Function _instance

lib/sqlalchemy/orm/loading.py:1068–1226

(row)

        is_not_primary_key = _none_set.intersection

    def _instance(row):
        # determine the state that we'll be populating
        if refresh_identity_key:
            # fixed state that we're refreshing
            state = refresh_state
            instance = state.obj()
            dict_ = instance_dict(instance)
            isnew = state.runid != runid
            currentload = True
            loaded_instance = False
        else:
            # look at the row, see if that identity is in the
            # session, or we have to create a new one
            identitykey = (
                identity_class,
                primary_key_getter(row),
                identity_token,
            )

            instance = session_identity_map.get(identitykey)

            if instance is not None:
                # existing instance
                state = instance_state(instance)
                dict_ = instance_dict(instance)

                isnew = state.runid != runid
                currentload = not isnew
                loaded_instance = False

                if version_check and version_id_getter and not currentload:
                    _validate_version_id(
                        mapper, state, dict_, row, version_id_getter
                    )

            else:
                # create a new instance

                # check for non-NULL values in the primary key columns,
                # else no entity is returned for the row
                if is_not_primary_key(identitykey[1]):
                    return None

                isnew = True
                currentload = True
                loaded_instance = True

                instance = mapper.class_manager.new_instance()

                dict_ = instance_dict(instance)
                state = instance_state(instance)
                state.key = identitykey
                state.identity_token = identity_token

                # attach instance to session.
                state.session_id = session_id
                session_identity_map._add_unpresent(state, identitykey)