def decompress(self, value):
        """
        Return the primary key value for the ``Select`` widget if the given
        recurrence rule exists in the queryset.
        """
        if value:
            try:
                pk = self.queryset.get(recurrence_rule=value).pk
            except self.queryset.model.DoesNotExist:
                pk = None
            return [pk, None, value]
        return [None, None, None]