Django model formset performance - django

Question

I have little perfomance issue with Django 1.4.2 and PostgreSQL 9.1. I want to create model fromset with form created like this:
forms.py
class AcknowledgeForm(forms.ModelForm):
class Meta:
model = Attendance
fields = ['acknowledge', ]
widgets = {'acknowledge': forms.CheckboxInput()}
AcknowledgeFormset = forms.models.modelformset_factory(Attendance, form=AcknowledgeForm, extra=0)
for model with few ForeignKeys
models.py
class Attendance(models.Model): #500k rows in DB
zamestnani = models.ForeignKey('people.Zamestnani', related_name='attendance') #~1k rows
day = models.ForeignKey(Day) #~2.5k rows
acknowledge = models.NullBooleanField(blank=True, null=True)
views.py
class VacationAcknowledgeView(LoginRequiredMixin, TemplateView):
template_name = "presence/presence_vacation_acknowledge.html"
http_method_names = ['get', 'post']
def get_context_data(self, **kwargs):
context = super(VacationAcknowledgeView, self).get_context_data()
person = Person.fromRequest(self.request)
first_day = date(date.today().year, 1, 1)
days = Attendance.objects.filter(acknowledge=None, day__date__gte=first_day, zamestnani__osoba=person)
context['formset'] = AcknowledgeFormset(queryset=days)
return context
def post(self, request, *args, **kwargs):
#next line is screwed
formset = AcknowledgeFormset(request.POST)
#never been there....
return super(VacationAcknowledgeView, self).get(request, *args, **kwargs)
I can create it, render it, everything seems ok, but assigning data from POST leads to server freeze for very looooong time (litteraly hours) for single object.
After short digging around I personaly blame model formset, because when I create it and process it just like single form, everything working as expected. But I have no idea how to fix/evade this.
Thank for any reasonable advice.

Answer 1

You mentioned that there are ~500,000 rows in your database for the Attendance models. In Django, when the queryset parameter is not specified for a ModelFormSet, it includes all objects in that model. Django is probably fetching all 500,000 rows of data.
You need to figure out the queryset for your ModelFormSet. E.g.
def post(self, request, *args, **kwargs):
queryset = Attendance.objects.none()
formset = AcknowledgeFormset(queryset=queryset, data=request.POST)
# continue with your regular code execution
The documentation contains a section for the queryset of a ModelFormSet: https://docs.djangoproject.com/en/1.9/topics/forms/modelforms/#django.forms.models.BaseModelFormSet