Annotate SUM aggregation value as field

[Vasiliy Maryutenkov]

Hello

How can I do this in Django without .extra() method?

SELECT SUM(column_1) AS total, column_1, column_2 FROM table

In your documentation you said that I should create the ticket if I use .extra() method, so I'm here

Model.objects.extra(select={'total': 'select sum(field) from model'})

And I also need to use this value in annotation, but it is not possible now :(

.annotate(q=F('field')/F('total'))

How can I do this?

[Simon Charette]

Using aggregate functions without a GROUP BY clause makes little sense, what do you expect SUM(field) to return if you plan on selecting field as well?

[Vasiliy Maryutenkov]

I need the total value of 'field' for percentage calculation

field / total

[Simon Charette]

If I understand you correctly you're after something along

queryset = Model.objects.annotate(
    total=Subquery(Model.objects.aggregate(Sum('field')),
    percent=F('field')/F('total'),
)

But that won't be possible until #28296 gets fixed.

In the mean time you can work around the issue by performing two queries. A first one to retrieve the aggregated sum and a second one to annotate the percentage on rows.

total = Model.objects.aggregate(total=Sum('field'))['total']
queryset = Model.objects.annotate(percentage=F('field')/total)