Improving the Django Query

Question

I am trying to optimize the following Django view.

def test_view(request, username):
  msgs = MyModel.objects.filter(name=username,
                                  created_at__range=[start_date, end_date]).order_by('-id')
  arr = []
  for msg in msgs:
    c = TestModel.objects.get(id=msg.test_id)
    if c not in arr:
        arr.append(c)

return render(request, "test.html", {'context': arr})

So I have two models.

• MyModel
• TestModel

Goal:

• Fetch only unique values on a column called test_id from MyModel ordered by id of MyModel .
• Need only two parameters from MyModel . They are test_id and created_at

Currently I can see the following ways to improve.

• Use values in filter query to get only test_id and created_at.
• Use the mysql Distinct keyword in Django to uniquely search on test_id
• Unnecessary looping through the data queryset.
• Again searching for collection in arr seems really unnecessary and time consuming.

I am relatively new to Django. So any help on how I should proceed or any links I should read would be appreciated.

Answer 1

I would suggest modifying your view as follows:

def test_view(request, username):
    msgs = MyModel.objects.filter(
        name=username, created_at__range=[start_date, end_date]
    ).order_by('-id').values_list('test_id', flat=True)

    arr = TestModel.objects.filter(id__in=msgs)

    return render(request, "test.html", {'context': arr})

That way you avoid just fetch all TestModel's you need in one query. Also, using values_list on MyModel query would allow to save memory since you don't use anything but test_id anyway.