django query all with filtering on the related set?

Question

class Customer(models.Model):
  name = models.CharField(max_length=200)
  # ..


class CustomerTicket(models.Model):
  customer = models.OneToOneField(Customer)
  date = models.DateTimeField(auto_now_add=True)
  # ..

I want to query all customers. And, adding for each customer its ticket if it has one in the date range - so I will get the ticket object only if it is in the given date range, otherwise the ticket field would be null.

Answer 1

Try this:

from django.db import models

customers = Customer.objects.select_related('customerticket').annotate(
    ticket=models.Case(models.When(models.Q(customerticket__date__gt=date1) & models.Q(customerticket__date__lt=date2), then=models.F('customerticket')))
)

And you will get ticket as a computed field. Note that when referencing relational fields such as ForeignKey or OneToOneField, F() returns the primary key value rather than a model instance, which means your ticket field will have value of the primary key.