[Django] #22850: False reverse accessor clash with inherited classes
Django
----------------------------------------------+------------------------
Reporter: semenov | Owner: nobody
Type: Uncategorized | Status: new
Component: Database layer (models, ORM) | Version: 1.7-beta-2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Consider the following `models.py`:
{{{#!python
class Base(models.Model):
field1 = models.IntegerField()
class Derived(Base):
field2 = models.IntegerField()
class Pointer(models.Model):
base = models.ForeignKey(Base)
derived = models.ForeignKey(Derived)
}}}
it crashes:
{{{
Unhandled exception in thread started by <function wrapper at 0x105daab90>
Traceback (most recent call last):
File
"/Users/semenov/work/project/venv/src/django/django/utils/autoreload.py",
line 170, in wrapper
fn(*args, **kwargs)
File
"/Users/semenov/work/project/venv/src/django/django/core/management/commands/runserver.py",
line 104, in inner_run
self.validate(display_num_errors=True)
File
"/Users/semenov/work/project/venv/src/django/django/core/management/base.py",
line 361, in validate
return self.check(app_configs=app_configs,
display_num_errors=display_num_errors)
File
"/Users/semenov/work/project/venv/src/django/django/core/management/base.py",
line 413, in check
raise CommandError(msg)
django.core.management.base.CommandError: System check identified some
issues:
ERRORS:
project.Pointer.derived: (fields.E304) Reverse accessor for
'Pointer.derived' clashes with reverse accessor for 'Pointer.base'.
HINT: Add or change a related_name argument to the definition for
'Pointer.derived' or 'Pointer.base'.
}}}
However, if I rewrite it to the semantically equivalent form:
{{{#!python
class AbstractBase(models.Model):
field1 = models.IntegerField()
class Meta:
abstract = True
class Base(AbstractBase):
pass
class Derived(AbstractBase):
field2 = models.IntegerField()
class Pointer(models.Model):
base = models.ForeignKey(Base)
derived = models.ForeignKey(Derived)
}}}
it works fine.
'''EXPECTED RESULT''': both cases should work identically (create
identical database tables and ORM accessors).
--
Ticket URL: <https://code.djangoproject.com/ticket/22850>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
Reporter: semenov | Owner: nobody
Type: Uncategorized | Status: new
(models, ORM) | 1.7-beta-2
Severity: Normal | Resolution:
Keywords: | Triage Stage:
Has patch: 0 | Unreviewed
Needs tests: 0 | Needs documentation: 0
Easy pickings: 0 | Patch needs improvement: 0
| UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by timo):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Comment:
Did the first version work in older versions of Django?
--
Ticket URL: <https://code.djangoproject.com/ticket/22850#comment:1>
Django
Reporter: semenov | Owner: nobody
Type: Uncategorized | Status: new
(models, ORM) | Resolution:
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by semenov):
* version: 1.7-beta-2 => 1.4
Comment:
I tested both cases on Django 1.4.X branch, the first version crashed with
similar error:
{{{
Unhandled exception in thread started by <bound method Command.inner_run
of <django.core.management.commands.runserver.Command object at
0x101e3b110>>
Traceback (most recent call last):
File "/Users/semenov/work/project/venv/lib/python2.7/site-
packages/django/core/management/commands/runserver.py", line 91, in
inner_run
self.validate(display_num_errors=True)
File "/Users/semenov/work/project/venv/lib/python2.7/site-
packages/django/core/management/base.py", line 270, in validate
raise CommandError("One or more models did not validate:\n%s" %
error_text)
django.core.management.base.CommandError: One or more models did not
validate:
project.pointer: Accessor for field 'derived' clashes with related field
'Derived.pointer_set'. Add a related_name argument to the definition for
'derived'.
}}}
The second version worked fine.
--
Ticket URL: <https://code.djangoproject.com/ticket/22850#comment:2>
Django
Reporter: semenov | Owner: nobody
Type: Uncategorized | Status: closed
Component: Database layer | Version: 1.4
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by timo):
* status: new => closed
* resolution: => invalid
Comment:
The two forms are really not equivalent -- they will created different
database tables. An explanation of the differences is
[https://docs.djangoproject.com/en/1.7/topics/db/models/#model-inheritance
here].
Having a ForeignKey to both Base and Derived in the first example in
really redundant as they will refer to the same database column
(`Base.id`). I believe that's the reason for the validation error.
--
Ticket URL: <https://code.djangoproject.com/ticket/22850#comment:3>