[Django] #28228: changing a primary key and saving results in a new object rather than renaming the existing object.
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Reporter: Chris | Owner: nobody
Withers |
Type: Bug | Status: new
Component: Database | Version: 1.11
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
See https://github.com/encode/django-rest-framework/issues/5158.
Incorrect behaviour in https://github.com/encode/django-rest-
framework/issues/5158#issuecomment-302679922.
Expected behaviour:
{{{#!python
MyModel.objects.all()
# <QuerySet [<MyModel: test>, <MyModel: test1>]>
instance = MyModel.objects.all()[0]
instance.name
# 'test'
instance.name = 'other test'
instance.save()
MyModel.objects.all()
# <QuerySet [<MyModel: test1>, <MyModel: other test>]>
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/28228>
Django <https://code.djangoproject.com/>
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Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(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
-------------------------------------+-------------------------------------
Comment (by Tom):
I think this is expected:
https://docs.djangoproject.com/en/1.11/topics/db/models/
''The primary key field is read-only. If you change the value of the
primary key on an existing object and then save it, a new object will be
created alongside the old one. For example...''
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:1>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Chris Withers):
Documenting buggy behaviour doesn't make it any less buggy. How are you
supposed to handle renames?
(Normal relational database behaviour is that change of the primary key
results in a change to the primary key, with cascading if so configured,
or an IntegrityError if not and there are foreign keys referring to this).
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:2>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Component: Database layer | Version: 1.11
(models, ORM) |
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
* status: new => closed
* resolution: => wontfix
Comment:
I wouldn't say it's a buggy behavior. It's well documented expected
behavior. See related tickets #17332, #14071.
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:3>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: closed
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Tim Graham):
I found [https://groups.google.com/d/topic/django-
developers/sCjjx6NmMw4/discussion an old proposal to deprecate the current
behavior]. Perhaps that conversation could be resumed -- I don't think
there's been any other recent discussion about it on the mailing list.
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:4>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: closed
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Marten Kenbeek):
You can change the primary key using `filter()` and `update()`:
{{{
MyModel.objects.filter(name='test1').update(name='other test')
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:5>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: closed
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Chris Withers):
@marten - I can, but I suspect that's exactly the kind of hack that the
DRF guys are reluctant to implement...
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:6>
Django
renaming the existing object.
-------------------------------------+-------------------------------------
Type: Bug | Status: closed
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Tom Christie):
I think the "wontfix" resolution against the ticket as stated makes sense.
However, there's a subset of this behavior that isn't documented, which is
the behavior when a primary key is **renamed to the value of an already
existing pk**.
Given this...
> If you change the value of the primary key on an existing object and
then save it, a new object will be created alongside the old one
I would expect to see the same behavior as if attempting to create a new
object with an already used pk. This *ought* to result in an integrity
error, given the uniqueness constraint.
The actual behavior currently is that the existing object will be
overwritten.
That doesn't seem like necessarily the most intuitive outcome, and it's
easy to see how it could introduce unexpected bugs or more-permissive-
than-intended behavior.
I haven't seen this specific subset of the issue isolated in any of the
related tickets/discussions, so I think there might be something worth
considering there.
--
Ticket URL: <https://code.djangoproject.com/ticket/28228#comment:7>