Re: [Django] #15807: order by 'pk' alias doesn't work with inherited models when parent has an ordering set

[Django]

#15807: order by 'pk' alias doesn't work with inherited models when parent has 
an
ordering set
-+-
   Reporter:  mat|  Owner:  nobody
   Type:  Bug| Status:  closed
  Milestone: |  Component:  Database layer
Version:  SVN|  (models, ORM)
 Resolution:  wontfix|   Severity:  Normal
   Triage Stage: |   Keywords:
  Unreviewed |  Has patch:  0
Needs documentation:  0  |Needs tests:  0
Patch needs improvement:  0  |  Easy pickings:  0
-+-
Changes (by jacob):

 * status:  new => closed
 * resolution:   => wontfix
 * easy:   => 0


Comment:

 So here's why this is happening:

 `pk` is translated to "the name of the primary key column". `Child`, as a
 concrete subclass, has a primary key that has a foreign key (technically a
 `OneToOneField` with `parent_link=True`) to `Foo`. In other words, your
 models, with the field implicitly added by the subclassing, ''actually''
 are like:

 {{{
 #!python
 class Foo(models.Model):
 bar = models.PositiveSmallIntegerField(default=1)

 class Child(models.Model):
 foo_ptr = models.OneToOneField(Foo, parent_link=True)
 barchild = models.PositiveSmallIntegerField(default=1)
 }}}

 This means that `Child.objects.order_by("pk")` actually translates to
 `Child.objects.order_by("foo_ptr")`. Remember, `foo_ptr` is a foreign key
 (one-to-one fields are just a special kind of foreign key). This is
 important, because `order_by("some_foreign_key")` translates to "order by
 the default ordering for the object pointed to by the foreign key". As
 [http://docs.djangoproject.com/en/dev/ref/models/querysets/#order-by the
 documentation says]:

   If you try to order by a field that is a relation to another model,
 Django will use the default ordering on the related model (or order by the
 related model's primary key if there is no Meta.ordering specified.

 The object pointed to, in this case, is `Foo`. So
 `Child.objects.order_by("pk")` is in fact working correctly, if a bit
 counterintuitively.

 We ''could'' change this, but it would introduce other subtle
 counterintuitive problems and would quite likely be backwards-
 incompatible. So I'm going to mark this wontfix. I know it's not ideal,
 but I'm afraid the cure is worse than the disease here.

-- 
Ticket URL: 
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Re: [Django] #15807: order by 'pk' alias doesn't work with inherited models when parent has an ordering set (was: 'pk' alias doesn't work with inherited models when parent has an ordering set)

[Django]

#15807: order by 'pk' alias doesn't work with inherited models when parent has 
an
ordering set
-+-
   Reporter:  mat|Owner:  nobody
   Type:  Bug|   Status:  new
  Milestone: |Component:  Database layer
Version:  SVN|  (models, ORM)
 Resolution: | Severity:  Normal
   Triage Stage: | Keywords:
  Unreviewed |Has patch:  0
Needs documentation:  0  |  Needs tests:  0
Patch needs improvement:  0  |
-+-
Changes (by mat):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


-- 
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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