id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
18432	Chained foreign keys with to_field produce incorrect query	Max Arnold	Spark23	"Example models:

{{{
class Model1(models.Model):
    pkey = models.IntegerField(unique=True, db_index=True)

class Model2(models.Model):
    model1 = models.ForeignKey(Model1, unique=True, to_field='pkey')

class Model3(models.Model):
    model2 = models.ForeignKey(Model2, unique=True, to_field='model1')
}}}

Steps to reproduce:

{{{
m1 = Model1(pkey=1000); m1.save(); m2 = Model2(model1=m1); m2.save(); m3 = Model3(model2=m2); m3.save()
(0.000) INSERT INTO `testcase_model1` (`pkey`) VALUES (1000); args=(1000,)
(0.000) INSERT INTO `testcase_model2` (`model1_id`) VALUES (1000); args=(1000,)
(0.000) INSERT INTO `testcase_model3` (`model2_id`) VALUES (1000); args=(1000,)

m3 = Model3.objects.get(model2=1000)
(0.001) SELECT `testcase_model3`.`id`, `testcase_model3`.`model2_id` FROM `testcase_model3` WHERE `testcase_model3`.`model2_id` = 1000 ; args=(1000,)

m3.model2
(0.000) SELECT `testcase_model2`.`id`, `testcase_model2`.`model1_id` FROM `testcase_model2` INNER JOIN `testcase_model1` ON (`testcase_model2`.`model1_id` = `testcase_model1`.`pkey`) WHERE `testcase_model1`.`id` = 1000 ; args=(1000,)
}}}

In the last query WHERE condition is incorrect - it does not respect to_field attribute and uses primary key instead.

Error message:
{{{
DoesNotExist                              Traceback (most recent call last)
/private/tmp/fkchain/<ipython-input-5-2fce98c5af10> in <module>()
----> 1 m3.model2

/Library/Python/2.7/site-packages/django/db/models/fields/related.pyc in __get__(self, instance, instance_type)
    313                 rel_obj = rel_mgr.using(db).get(**params)
    314             else:
--> 315                 rel_obj = QuerySet(self.field.rel.to).using(db).get(**params)
    316             setattr(instance, cache_name, rel_obj)
    317             return rel_obj

/Library/Python/2.7/site-packages/django/db/models/query.pyc in get(self, *args, **kwargs)
    347         if not num:
    348             raise self.model.DoesNotExist(""%s matching query does not exist.""
--> 349                     % self.model._meta.object_name)
    350         raise self.model.MultipleObjectsReturned(""get() returned more than one %s -- it returned %s! Lookup parameters were %s""
    351                 % (self.model._meta.object_name, num, kwargs))

DoesNotExist: Model2 matching query does not exist.
}}}"	Bug	closed	Database layer (models, ORM)	1.3	Normal	fixed			Ready for checkin	1	0	0	0	0	0