Django add aggregate operation to a query result - django

Question

I'm trying to do an aggregate operation between two tables using Django, my models are:
class Cusinetype(models.Model):
hometype_en = models.TextField()
active = models.BooleanField()
hometype_es = models.TextField(blank=True, null=True)
class Meta:
managed = False
db_table = 'cusinetype'
class Foodpreferences(models.Model):
id_client = models.ForeignKey(Client, models.DO_NOTHING, db_column='id_client')
id_cusinetype = models.ForeignKey(Cusinetype, models.DO_NOTHING, db_column='id_cusinetype')
created_at = models.DateTimeField()
class Meta:
managed = False
db_table = 'foodpreferences'
The query that I'm trying to build is:
SELECT
ct.id,
ct.hometype_en,
ct.hometype_es
,
((SELECT COUNT(*)
FROM foodpreferences fp
WHERE fp.id_cusinetype = ct.id AND fp.id_client = 3 ) > 0 ) selected
FROM
Cusinetype ct
I'm trying to generate a model, to store the information of those tables in a single one query, but anything works.
Someone has an idea about how to do it?

Answer 1

serializers.py
class PreferencesSerializer(serializers.ModelSerializer):
selected = serializers.IntegerField()
class Meta:
model = Cusinetype
fields = ('id', 'trucktype_en', 'trucktype_es', 'selected')
views.py
qs = Cusinetype.objects.filter().filter(active = True)
qs = qs.annotate(
selected=Sum(Case(
When(foodpreferences__id_client=3, then=1),
output_field=IntegerField()
))
)
serializers = PreferencesSerializer(qs, many = True)
return Response({ "result": serializers.data })