I don't know if this will make you happy but when I researched this some months ago I found no good solution. During my search I came upon the following pages that sort of relate to this...
- http://github.com/dcramer/django-idmapper - http://appengine-cookbook.appspot.com/recipe/high-concurrency-counters-without-sharding/ - http://pastie.org/615863 - http://stackoverflow.com/questions/3522827/handling-race-condition-in-model-save-django I ended up using something similar to the stackoverflow solution. I needed to generate a new number per "produced_at" date in a model called Entity and ended up with the following custom .save method. This is a pretty rough copy-paste so things might not work out of the box but the principle is there. class Entity(models.Model): ... created_at = models.DateTimeField(auto_now_add=True) produced_at = models.DateField(default=datetime.now) number = models.PositiveIntegerField(default=1) class Meta: unique_together=(('produced_at', 'number')) def save(self, *args, **kwargs): if self.id: #do a normal save super(Entity, self).save(*args, **kwargs) return while not self.id: try: max = Entity.objects.filter(produced_at=self.produced_at).aggregate(Max('number')) if max['number__max']: self.number = max['number__max']+1 else: self.number=1 #Trying to save with number = self.number super(Entity, self).save(*args, **kwargs) except IntegrityError: # conflicting number, chill out and try again sleep(uniform(0.1, 0.6)) #chill out, then try again # try again then -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
