Django queryset.filter() does not work on intersection() result

Question

I'm having issues with queryset.intersection(...).filter(...) . I found that the filter() call does simply not do anything, but returns the same results as the queryset.intersection() .

I now present an illustrative example. minex/models.py file:

from uuid import uuid4

from django.db import models


class Channel(models.Model):
    name = models.CharField(max_length=255)


class Release(models.Model):
    version = models.CharField(max_length=255)
    uuid = models.CharField(max_length=100, default="")
    channels = models.ManyToManyField(to=Channel, related_name='releases')

    def save(self, *args, **kwargs):
        if not self.uuid:
            self.uuid = str(uuid4())

        super(Release, self).save(*args, **kwargs)


class Serial(models.Model):
    name = models.CharField(max_length=255)
    releases = models.ManyToManyField(to=Release, related_name='serials', blank=True)

Illustration of the problem: dbtest.py

import os
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'minexample.settings')
from minexample.wsgi import application
from minex.models import Serial, Release, Channel

channel = Channel.objects.create(name="stable")

r1 = Release.objects.create(version="1.0")
r1.channels.add(channel)
r06 = Release.objects.create(version="0.6.2")
r06.channels.add(channel)

serial = Serial.objects.create(name="Some Serial")
serial.releases.add(r06)

releases = serial.releases.all().intersection(channel.releases.all())

assert r1 not in releases  # works as expected

assert not releases.filter(uuid=r1.uuid).exists()  # assertion failed... why?

Note: the last assertion does not fail if we instead did releases = serial.releases . The problem seems to be that I'm calling intersection() . I also stepped into Django's code and the WHERE statement does not contain the uuid=r1.uuid at all... Is this a bug or am I doing something wrong?

Answer 1

Django now gives an error informing that filter() is not supported after applying intersection() :

https://code.djangoproject.com/ticket/31227