#33209: ManyToManyField.add() doesn't respect a unique constraint in
intermediate
table
-------------------------------------+-------------------------------------
Reporter: Yuta Okamoto | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 3.1
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
I'll let others chime in but I think this is invalid.
`ManyToManyField` was designed to allow only a single instance of the
relationship it defines and not allow extra dimensions to be considered.
In your case that means a single instance of the `Member <-> Company`
many-to-many relationship can be tracked at a time and the `role`
dimension is not taken into account at all.
If you want to keep using `ManyToManyField` for this purpose you'll likely
need to tweak your data model a bit
e.g.
{{{#!python
class Company(models.Model):
pass
class Role(models.Model):
company = models.ForeignKey(Company, related_name='roles')
class Member(models.Model):
roles = models.ManyToManyField(Role, related_name='members')
@property
def companies(self):
return Company.objects.filter(roles__members=self)
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/33209#comment:6>
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