Multiple annotations in one query

[David]

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

[Matthew Pava]

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

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[David]

Thanks Matthew will take a look.

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