How to Get queryset not dict django aggregate-CodePudding

i'm using this queryset for my requirements

invoices = Invoice.objects.aggregate(total_amount=Sum('order__order_items__amount'),number_of_invoices=Count('pk', distinct=True))

which returns dict--->

{'total_amount': Decimal('17700.00'), 'number_of_invoices': 2}

but I want queryset how can i do that.. Thanks for any help

CodePudding user response：

This is what aggregate do :)

You can add a DecimalField to Invoice model, that aggregates total_amount during before every save. I suggest signals for that.

apps.py

class YourAppConfig(AppConfig):
    ...

    def ready(self):
        from . import signals

signals.py

from django.db.models.signals import pre_save
from django.dispatch import receiver

from .models import Invoice

@receiver(pre_save, sender=Invoice)
def total_amount_aggregation(sender, instance, *args, **kwargs):
    instance.total_amount = # aggregate desired amount here

You have to set similar signals for your Order, so if you change Order object, the related Invoice object will be recalculated.

After that QuerySet will stay as QuerySet and every object will have always caclulated field.

CodePudding user response：

Instead of using .aggregate(...) use .annotate(...) this will return a QuerySet with given expression

from django.db.models import Sum, Count

invoices = Invoice.objects.annotate(
            total_amount=Sum('order__order_items__amount'),
            number_of_invoices=Count('pk', distinct=True)
           )

then to get Sum(...) & Count(...) of field then do like this invoices[0].total_amount__sum & invoices[0].number_of_invoices__count