since this turns up first I thought I'd post my quick & dirty solution
here for the copy-pasters of the interwebs:
def children(self):
class Union(object):
def __init__(self, cmp_on, sources):
self._sources = sources
self._tops = [None] * len(sources)
self._cmp_on = cmp_on
def next(self):
min_i, min = -1, None
for i, top in enumerate(self._tops):
if not top:
try:
top = self._sources[i].next()
except StopIteration:
top = StopIteration
self._tops[i] = top
if not top == StopIteration:
if min == None:
min = top
min_i = i
else:
if getattr(top, self._cmp_on) < getattr
(min, self._cmp_on):
min = top
min_i = i
if min == None:
raise StopIteration
self._tops[min_i] = None
return min
def __iter__(self):
return self
return Union('title', [
iter(self.page_set.order_by('title').all()),
iter(self.directory_set.order_by('title').all())])
On Nov 20 2008, 1:59 am, Malcolm Tredinnick <[email protected]>
wrote:
> On Wed, 2008-11-19 at 11:04 -0800, Luke Seelenbinder wrote:
> > the models are:
>
> > class Word(models.Model):
> > ... some stuff...
>
> > class Meta:
> > abstract=True
> > class Noun(Word):
> > .. some stuff ..
> > class Verb(Word):
> > ... some stuff ...
>
> > code:
>
> > nouns= Noun.objects.all()
> > verbs=Verb.objects.all()
>
> > words = verbs | nouns
>
> > I get an error saying: "Cannot combine queries on two different base
> > models."
> > is there anyway to accomplish this,
>
> Not at the SQL level. Doing a union of two completely distinct result
> sets like this is not really a common enough operation to warrant to
> extra complexity in Django's ORM. Realise that, in the general case, the
> two querysets could have completely different sets of columns and
> everything.
>
> The simplest way to achieve the same effect is order each Queryset
> individually. Then you'll have two Python iterators (a queryset is an
> iterator) that are sorted appropriately and you just need to merge the
> results together into a final sorted iterator. In other words, you're
> doing a merge (or tape) sort where you've already sorted the individual
> sub-piles.
>
> Regards,
> Malcolm
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