#34207: Incorrect SQL query when adding a ManyToMany related object with a
"through" table prevents adding a new relationship if the new relationship
is identical except for a different value for "through_defaults"
-------------------------------------+-------------------------------------
Reporter: Credentive | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 4.1
(models, ORM) |
Severity: Normal | Resolution: duplicate
Keywords: ManyToManyField | Triage Stage:
through | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Simon Charette):
> Your example documentation strongly suggests otherwise
Could you elaborate on that? From what I can read none of the examples you
linked suggest that `add` supports this feature?
There is effectively a section that points at the fact that
`remove(related)` will remove all entries matching the `(from, to)` tuple
but defined by the many-to-many
In the example you've just provided you don't use `members.add` to add the
second relationship to Ringo but rely on explicit `Membership` creation
which is supported.
To make it clear, intermediary models that don't define a strict unique
relationship on `(from, to)` are supported. However
`add(through_defaults)` is focused on enforcing that at least one entry of
the `(from, to)` tuple exists and doesn't make any assumption with regards
to the unique constraints defined on the intermediary model.
If you want to enforce the unique existence of a tuple that is a superset
of the the `(from, to)` relationship you should use `get_or_create`
instead of expecting `add(through_defaults)` to figure out which of your
unique constraints should be enforced based on your provided
`through_defaults`.
--
Ticket URL: <https://code.djangoproject.com/ticket/34207#comment:3>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/01070184fd40df1d-fecd7b51-9ea7-4ce1-8e39-d97b976c8ecc-000000%40eu-central-1.amazonses.com.
