Aggregation of an annotation in GROUP BY in Django

Question

UPDATE

Thanks to the posted answer, I found a much simpler way to formulate the problem. The original question can be seen in the revision history.

Answer 1

This is expected from the way group_by works in Django. All annotated fields are added in GROUP BY clause. However, I am unable to comment on why it was written this way.

You can get your query to work like this:

Title.objects
  .values('publisher')
  .annotate(total_dbl_price=Sum(2*F('price'))

which produces following SQL:

SELECT publisher, SUM((2 * price)) AS total_dbl_price
FROM title
GROUP BY publisher

which just happens to work in your case.

I understand this might not be the complete solution you were looking for, but some even complex annotations can also be accommodated in this solution by using CombinedExpressions(I hope!).