ManyToMany clear doesn't clear the items from the object but deletes from db

[Sharat M R]

class Media(models.Model):
    name = models.CharField(max_length=100)


class Tag(models.Model):
    tag = models.CharField(max_length=100)
    medias = models.ManyToManyField(Media)

    def __unicode__(self):
        return self.tag

Assume tag object below already has three items of Media model in medias which are saved in db. [m1, m2, m3].

tag = Tag.objects.get(id=1)
tag.medias.clear()
print(tag.medias.all())

The above code prints all the three [m1, m2, m3]. Fetching the tag again using get and printing givens an empty list "[ ]"

Failing Testcase

class Test(TestCase):
    def test(self):
        tag = Tag.objects.create(tag='Tag')
        tag.medias.create(name='A')
        tag.medias.create(name='B')
        tag.medias.create(name='C')
        tag = Tag.objects.prefetch_related('medias').get(id=1)
        tag.medias.clear()
        print(tag.medias.all())

I guess its related to prefetch_related function.

[Tim Graham]

I can't reproduce that. Here's my complete test case:

from django.test import TestCase

from .models import Tag


class Test(TestCase):
    def test(self):
        tag = Tag.objects.create(tag='Tag')
        tag.medias.create(name='A')
        tag.medias.create(name='B')
        tag.medias.create(name='C')
        tag = Tag.objects.get(id=1)
        tag.medias.clear()
        print(tag.medias.all())

Also, Django's test suite ​tests the behavior.

Please reopen if you can provide a failing test case.

[Sharat M R]

class Test(TestCase):
    def test(self):
        tag = Tag.objects.create(tag='Tag')
        tag.medias.create(name='A')
        tag.medias.create(name='B')
        tag.medias.create(name='C')
        tag = Tag.objects.prefetch_related('medias').get(id=1)
        tag.medias.clear()
        print(tag.medias.all())

This test print all the three medias for me