#26706: ManyToMany clear doesn't clear the items from the object but deletes
from
db
-------------------------------------+-------------------------------------
Reporter: cosmosgenius | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.8
(models, ORM) |
Severity: Normal | Resolution:
Keywords: manytomany, m2m, | Triage Stage:
clear | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by cosmosgenius):
* status: closed => new
* resolution: worksforme =>
Old description:
> {{{
>
> 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 "[ ]"
New description:
{{{
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.
--
Comment:
{{{
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())
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/26706#comment:2>
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