Django custom SimpleListFilter - django

Question

I have this two models:
class Intervencao(models.Model):
.......
class Alvaras(models.Model):
intervencao = models.ForeignKey(Intervencao, related_name='IntervencaoObjects2',on_delete=models.CASCADE)
data_alv = models.DateField(blank=True,null=True,verbose_name="Data do alvaras")
I want to add a custom filter in my Intervencao.Admin, that do a query to the last record i have in Alvaras and check if the field data_alv it is empty or not. I already got it working, but i want only the last record.
class Dataalv(admin.SimpleListFilter):
title = ('data de alvaras')
parameter_name = 'data_alv'
def lookups(self, request, model_admin):
return (
('yes', 'yes'),
('no', 'no')
)
def queryset(self, request, queryset):
value = self.value()
if value == 'yes':
return queryset.filter(IntervencaoObjects2__data_alv__isnull=False)
elif value == "no":
return queryset.filter(IntervencaoObjects2__data_alv__isnull=True)
class IntervencaoAdmin(admin.ModelAdmin):
list_filter = Dataalv,

Answer 1

Here is a solution using Subquery:
from django.db.models import OuterRef, Subquery
class Dataalv(admin.SimpleListFilter):
title = ('data de alvaras')
parameter_name = 'data_alv'
def lookups(self, request, model_admin):
return (
('yes', 'yes'),
('no', 'no')
)
def queryset(self, request, queryset):
value = self.value()
qs = queryset.annotate(
data_alv=Subquery(
(Alvaras.objects
.filter(intervencao_id=OuterRef('id'))
.order_by('-id')
.values('data_alv')[:1]
)
)
)
if value == 'yes':
return qs.filter(data_alv__isnull=False)
if value == "no":
return qs.filter(data_alv__isnull=True)