[Fixed]-Django .aggregate() on .annotate()

I think medmunds is right, you cannot re-use the same name for annotate and aggregate alias. This is what you want to do, I think:

articles = metrics_models.Article.objects.filter(
    state__date__month=month,
    state__date__year=year
).annotate(
    min_views=Min('state__views'),
    min_downloads=Min('state__downloads')
).aggregate(
    sum_min_views=Sum('min_views'),
    sum_min_downloads=Sum('min_downloads')
)

based on your original query, i think this would work.

from django.db.models import ExpressionWrapper, Min, OuterRef

articles = (
    Article.objects.filter(state__date__month=month, state__date__year=year)
    .annotate(
        views=ExpressionWrapper(
            Min(
                State.objects.filter(article_id=OuterRef("id")).values_list(
                    "views", flat=True
                )
            ),
            output_field=models.IntegerField(),
        ),
        downloads=ExpressionWrapper(
            Min(
                State.objects.filter(article_id=OuterRef("id")).values_list(
                    "downloads", flat=True
                )
            ),
            output_field=models.IntegerField(),
        ),
    )
    .aggregate(views=Sum("views"), downloads=Sum("downloads"))
)

When you use the same field name for both the annotate() method and the aggregate() method, you are creating a new field with that name on each object in the queryset and then trying to get the sum of that field.

However, the new field created by the annotate() method is not the same as the field being passed to the aggregate() method.

The annotate() method creates a new field on each object in the queryset that contains the result of the computation, and this field is not stored in the database, it only exists in the queryset in memory.

On the other hand, the field passed to the aggregate() method is a reference to a field stored in the database/queryset, and it’s used to get the sum of the values stored in the database.

So when you use the same field name for both annotate() and aggregate() methods, you are trying to sum up the values of a field that only exists in memory (the one you declared on the aggregate method overrides the one from annotate), not in the database/queryset. This is why you are not getting the expected result.