CODEWITHSUNDEEP
djangodjango-models
marzique
marzique

Reputation: 694

Django annotate by foreign key's date field but exclude past dates

I want to have my queryset of Card model annotated with new field called available_on, which should be calculated as closest date in future of relative Booking model's field removal_date. It should consider only dates in future, how can I filter out removal_date dates that are in the past? What I have now is this.

def with_available_on(self):
    qs = self.annotate(available_on=Case(
        When(
            bookings_count__gt=0,
            slots_available__lt=1, 
            then=Min('bookings__removal_date')),
            default=None
        )
    )
    return qs

Also I want it to be calculated on database side if possible for performance purposes. Thanks

Upvotes: 1

Views: 311

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476584

You can use the filter=… parameter [Django-doc] to filter the objects over which you span the aggregate in the Min aggregate [Django-doc]:

from django.db.models import Q
from django.db.models.functions import Now

def with_available_on(self):
        qs = self.annotate(available_on=Case(
            When(
                bookings_count__gt=0, slots_available__lt=1,
                then=Min(
                    'bookings__removal_date',
                    filter=Q(bookings__remval_date__gte=Now())
                )
            ),
            default=None)
        )
        return qs

Upvotes: 2

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