Filtering on a relation whose model has a different PK type doesn't work

[David Gouldin]

Using the following models:

class Author(models.Model):
    name = models.CharField(max_length=255)

class Book(models.Model):
    name = models.CharField(max_length=50, primary_key=True)
    author = models.ForeignKey(Author)

The following code fails:

In [1]: a = Author.objects.create(name='Me')

In [2]: b = Book.objects.create(name='My Book', author=a)

In [3]: Author.objects.filter(book=b)
....
ValueError: invalid literal for int() with base 10: 'My Book'

This seems to be the source of the problem:

​http://code.djangoproject.com/browser/django/trunk/django/db/models/fields/related.py?rev=13037#L190

_pk_trace uses field.rel.to to resolve the field to use for prepping the filter value. In the case above, It's preparing Book.pk (a CharField) as if it were a value for Author.pk (an AutoField) and blows up when casting the string to an int. I'm not sure how best to go about solving the issue. _pk_trace doesn't currently have any way I know of to tell which side of the relation the value arg is coming from.

[David Gouldin]

I actually found this while researching a fix for #13383. I don't think that ticket can be properly fixed until this one is resolved.

[Karen Tracey]

I believe this is the same root problem as what is described in #11319.

[Ole Laursen]

The fix for 11319 unfortunately didn't fix this. :( I have this problem 1.2.7 and 1.3.1. This is a regression from 1.1.1 which works fine.

[Aymeric Augustin]

I can confirm the problem. I'm attaching a test case. The tests fails with trunk; but if I remove , foreign_key=True in the definition of the Book model, it passes.

[Olivier Le Thanh Duong]

Look's like this was fixed in 97774429aeb54df4c09895c07cd1b09e70201f7d