#26320: Multi-table inheritance pointer merged with another OneToOneField
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Reporter: BertrandBordage | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Suppose we have these models:
{{{#!python
class Parent(Model):
pass
class Child(Parent):
parent_ptr2 = OneToOneField(Parent, null=True, related_name='+')
}}}
`Child` should have two `OneToOneField`s, `parent_ptr` and `parent_ptr2`.
Unfortunately, Django has a critical issue where it merges these two
fields into this:
{{{#!python
parent_ptr2 = OneToOneField(Parent, primary_key=True, null=True,
related_name='+')
}}}
And of course, a nullable primary key is impossible, so we can’t even do a
migration: `fields.E007` is raised.
But defining without multi-table inheritance exactly the same model – in
terms of database definition – works just fine:
{{{#!python
class WorkingModel(Model):
parent_ptr = OneToOneField(Parent, primary_key=True, related_name='+')
parent_ptr2 = OneToOneField(Parent, null=True, related_name='+')
}}}
So multi-table inheritance is probably what causes this confusion.
This bug is present on all supported Django versions, from 1.8 to 1.9.3.
I guess this can be seen as a release blocker, there is no regression but
this is quite critical (and blocking, in my case).
--
Ticket URL: <https://code.djangoproject.com/ticket/26320>
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