Django save() does not work - mysql

Question

I'm writing an elections application. In the process, I've defined an Election model and a Candidate model.
Note: I'm using Django version 1.3.7, Python 2.7.1.
One of Election's methods,
Election.count_first_place(self)
is intended to count the number of first place votes each candidate receives and update the candidates' numVotes attribute. But for some reason they all stay at zero, no matter the ballots.
Note: I'm implementing STV so each ballot contains an array(ballot.voteArray) of Candidates in order of most preferred (position zero) to least preferred (position n). I've implemented this list with a PickledObjectField (see link).
models.py
class Candidate(models.Model):
election = models.ForeignKey("Election")
numVotes = models.FloatField(blank=True)
class Ballot(models.Model):
election = models.ForeignKey("Election", related_name = "ballot_set")
voteArray = PickledObjectField(null=True,blank=True)
class Election(models.Model):
position = models.CharField(max_length = 50)
candidates = models.ManyToManyField(Candidate,related_name="elections_in",null=True,blank=True)
def count_first_place(self):
#retrieve all of the ballots cast in this election
ballots = Ballot.objects.filter(election = self)
for ballot in ballots.all():
# the first element of a ballot's voteArray is a Candidate object
first_place_choice = ballot.voteArray[0]
first_place_choice.numVotes += 1
first_place_choice.save()
ballot.save()
self.save()
Here is what happens when I run a test:
Note: I realize that I am saving way more often than is necessary. Just being absolutely sure while I test this thing that it saves when it needs to.
elec = Election(position="Student Body President")
elec.save()
j = Candidate(election=elec,numVotes=0)
j.save()
e = Candidate(election=elec,numVotes=0)
e.save()
b = Candidate(election=elec,numVotes=0)
b.save()
elec.candidates.add(j,e,b)
elec.save()
ballot1 = Ballot(election=elec,voteArray=[j,e,b])
ballot1.save()
ballot2 = Ballot(election=elec,voteArray=[j,b,e])
ballot2.save()
ballot3 = Ballot(election=elec,voteArray[e,b,j])
ballot3.save()
So after this bit, j has two 2 place votes, and e has 1. But when I run
elec.count_first_place()
j still has zero votes, as do e and b.
What's up with that????

Answer 1

This is a very strange table structure. Pickling other model instances is a very bad idea: the pickled versions will not update when their database rows do. Really you should be storing an array of candidate IDs, or even better create a many-to-many relationship from Ballot to Candidate with a through table indicating position.
But I think your problem is simpler than that. You say that the objects still have zero votes: that is because you have not updated those particular instances. Again, there is no direct relationship between a Django instance and the database row, other than on loading and saving. You'll need to reload the objects from the database to see any updates.