I am trying to use Django's reverse generic relation for accessing and filtering related objects via Django's ORM. See below declared models:
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.db import models
class Status(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
class Package(models.Model):
name = models.CharField(max_length=500)
status = models.ForeignKey(Status, on_delete=models.PROTECT)
hst_entries = GenericRelation("myapp.StatusHistory", related_query_name="package")
def __str__(self):
return self.name
class StatusHistory(models.Model):
content_type = models.ForeignKey(ContentType, on_delete=models.PROTECT)
object_id = models.TextField()
object = GenericForeignKey("content_type", "object_id")
status = models.ForeignKey(Status, on_delete=models.PROTECT)
entry_added = models.DateTimeField(auto_now_add=True)
def __str__(self):
return f"{self.content_type} - {self.object_id}: {self.status.name}"
As you see there is generic relation between Package and StatusHistory models. For accessing related packages from StatusHistory model I tried:
StatusHistory.objects.filter(package__name__startswith="pack")
And result:
ProgrammingError: operator does not exist: text = integer
LINE 1: ...kage" ON ("myapp_statushistory"."object_id" = "myapp...
^
HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
I understand that PostgreSQL is complaining about type mismatch between object_id (of StatusHistory model) and id (of Package model) fields. This mismatch can be solved by PostgreSQL cast operator :: as below:
### WRONG
join myapp_package on (myapp_statushistory.object_id = my_app_package.id)
### RIGHT
join myapp_package on (myapp_statushistory.object_id = my_app_package.id::varchar)
Is there possible way to make such casting via Django's ORM?
Note: Converting object_id field to IntegerField is not an option for me.