Say I have 2 models:
class Poll(models.Model):
category = models.CharField(u"Category", max_length = 64)
[...]
class Choice(models.Model):
poll = models.ForeignKey(Poll)
[...]
Given a Poll object, I can query its choices with:
poll.choice_set.all()
But, is there a utility function to query all choices from a set of Poll?
Actually, I'm looking for something like the following (which is not supported, and I don't seek how it could be):
polls = Poll.objects.filter(category = 'foo').select_related('choice_set')
for poll in polls:
print poll.choice_set.all() # this shouldn't perform a SQL query at each iteration
I made an (ugly) function to help me achieve that:
def qbind(objects, target_name, model, field_name):
objects = list(objects)
objects_dict = dict([(object.id, object) for object in objects])
for foreign in model.objects.filter(**{field_name + '__in': objects_dict.keys()}):
id = getattr(foreign, field_name + '_id')
if id in objects_dict:
object = objects_dict[id]
if hasattr(object, target_name):
getattr(object, target_name).append(foreign)
else:
setattr(object, target_name, [foreign])
return objects
which is used as follow:
polls = Poll.objects.filter(category = 'foo')
polls = qbind(polls, 'choices', Choice, 'poll')
# Now, each object in polls have a 'choices' member with the list of choices.
# This was achieved with 2 SQL queries only.
Is there something easier already provided by Django? Or at least, a snippet doing the same thing in a better way.
How do you handle this problem usually?