a weird mishmash of doing an SQL "IN (x, y, z)" and covering consecutive ranges. For Django. Using Q objects and horrifying machinations.

lolwut.py

def generate_integer_pk_range(flat_iterable):
    """
    A bit of this is taken from :
    http://code.activestate.com/recipes/496682-make-ranges-of-contiguous-numbers-from-a-list-of-i/#c2
    and a bit from:
    https://github.com/kezabelle/django-inheritrix/blob/a4825612dbcc20add509c4bb49e93bdb1f8f409f/inheritrix.py#L44
    
    >>> x = MyModel.objects.values_list('pk', flat=True)
    [1, 2...5, 9, 100...121]
    >>> y = generate_integer_pk_range(x)
    Q(pk=1) | Q(pk__range=(2, 5)) | Q(pk=9) | Q(pk__range=(100, 121)
    >>> z = MyModel.objects.filter(y)
    
    Would need expanding to cover supplying a related lookup.
    """
    def yielder():
        flat_iterable_sorted = sorted(set(flat_iterable))
        leftovers = set()
        for k, g in groupby(enumerate(flat_iterable_sorted), lambda (i,x):i-x):
            result = map(operator.itemgetter(1), g)
            num_in_result = len(result)
            if num_in_result > 1:
                first = result[0]
                last = result[-1]
                yield Q(pk__range=(first, last))
            else:
                leftovers.add(result[0])
        if leftovers:
            yield Q(pk__in=leftovers)
    out = reduce(operator.or_, yielder())
    return out