Django ORM JOIN query

Question

I've 2 models

class ShipmentBagSealMapping(models.Model):
    bag_seal = models.CharField(max_length = 255)
    status = models.CharField(max_length = 255, default = 'open')
    time = models.DateTimeField( auto_now_add = True, db_index = True)
    shipment_id = models.ForeignKey('Shipment', related_name = 'bags')



class Shipment(models.Model):
    job_id = models.CharField(max_length = 255)
    time = models.DateTimeField( auto_now_add = True, db_index = True)

I want to write a JOIN query which tells me the count of records in ShipmentBagSealMapping with status = close and time of Shipment is in range [start_time and end_time].

Here' what I tried:

total_bags = ShipmentBagSealMapping.objects.filter(shipments__time__range = [start_time,end_time],status='close').values('bag_seal').distinct().count()

But it throws an error saying :-

Cannot resolve keyword 'shipments' into field. Choices are: bag_seal, id, shipment_id, status, time

How do I do it?

Answer 1

This should do it:

total_bags = ShipmentBagSealMapping.objects.filter(shipment_id__time__range = [start_time,end_time],status='close').values('bag_seal').distinct().count()

See you have defined the field as shipment_id not shipments

Answer 2

Django will automatically add _id in your ForeignKey, so make some change like this may help

class ShipmentBagSealMapping(model.Model):
bag_seal = models.CharField(max_length = 255)
status = models.CharField(max_length = 255 )
time = models.DateTimeField( auto_now_add = True)
shipments = models.ForeignKey('Shipment', related_name = 'bags')