Re: Multiple annotations in one query

Thanks Matthew will take a look.

On Monday, 24 September 2018 15:40:44 UTC+1, Matthew Pava wrote:

Hi David,

Performing multiple annotations on a queryset is not the same as combining multiple aggregations.

Saying that, if you truly are getting wrong results, you could try using the Window functions or the Subquery object.

https://docs.djangoproject.com/en/2.1/ref/models/database-functions/#window-functions

https://docs.djangoproject.com/en/2.1/ref/models/expressions/#subquery-expressions

 

 

From: django...@googlegroups.com [mailto:django...@googlegroups.com] On Behalf Of David
Sent: Monday, September 24, 2018 9:36 AM
To: Django users
Subject: Multiple annotations in one query

 

Hi

 

I understand that performing multiple annotations on a queryset will produce incorrect results, I was wondering how anyone else gets around this?

 

"Combining multiple aggregations with annotate() will yield the wrong results because joins are used instead of subqueries"

 

My query for example:

 

        data = Client.objects.filter(

                case=self.kwargs['case_pk']

            ).select_related(

            'case', 'inheritance',

            ).prefetch_related(

                'children_set', 'stepchildren_set',

                'grandchildren_set', 'property_set',

                'investment_set', 'insurance_set',

                'liability_set', 'lumpsumdeathinservice_set',

            ).annotate(

                property_sum=Sum('property__value',),

                investment_sum=Sum('investment__value'),

                insurance_sum=Sum('insurance__value'),

                liability_sum=Sum('liability__value'),

                lumpsumdeathinservice_sum=Sum('lumpsumdeathinservice__value'),

            ).order_by(

                'last_name', 'first_name'

            )

 

 

I need to get the sum'd values.

 

Will I have to query each model individually and annotate it? and then somehow merge the querysets?

 

Thanks

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