Atomic operations in Django?

Question

I\'m trying to implement (what I think is) a pretty simple data model for a counter:

class VisitorDayTypeCounter(models.Model):
    visitType = models.CharFi         


        

Answer 1

Two suggestions:

Add a unique_together to your model, and wrap the creation in an exception handler to catch duplicates:

class VisitorDayTypeCounter(models.Model):
    visitType = models.CharField(max_length=60)
    visitDate = models.DateField('Visit Date')
    counter = models.IntegerField()
    class Meta:
        unique_together = (('visitType', 'visitDate'))

After this, you could stlll have a minor race condition on the counter's update. If you get enough traffic to be concerned about that, I would suggest looking into transactions for finer grained database control. I don't think the ORM has direct support for locking/synchronization. The transaction documentation is available here.