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
10417	Some model instances returned from a query set do not have any attributes filled in.	Kevin Van Wilder	nobody	"By combining two Q functions in my queryset with a OR (|) relation between them over a multi-table inherited model, i get the following bug:

== Example of bug ==

{{{
>>> p = Project.objects.get(pk=1)

>>> for member in StaffMember.objects.all().filter(Q(publications_as_author__belongsTo = p) | Q(publications_as_coauthor__belongsTo = p)):
... 	print member.pk
... 
3
4

>>> for member in StaffMember.objects.all().filter(Q(publications_as_author__belongsTo = p) | Q(publications_as_coauthor__belongsTo = p)):
... 	print member.first_name
... 
Sven
None # << the bug, should be ""Kevin"". as proven on the line below.

>>> member = StaffMember.objects.get(pk=4)
>>> member.first_name
u'Kevin'
}}}


rozwell from #django had the following to say about this bug:
01:24 < rozwell> so it seems to me that this is happening when the queryset gets collapsed into a list of model instances

== Necessary information to reproduce bug ==


{{{
class Publication(models.Model):
	titled = models.CharField(max_length=255)
	co_authors = models.ManyToManyField('StaffMember', related_name=""publications_as_coauthor"")
	belongsTo = models.ManyToManyField('Project', related_name=""has_publications"")
	authors = models.ManyToManyField('StaffMember', related_name=""publications_as_author"")

admin.site.register(Publication)

class Project(models.Model):
	named = models.CharField(max_length=255)
	hasStaffMembers = models.ManyToManyField('StaffMember', related_name=""workson"")

admin.site.register(Project)

class Person(models.Model):
	first_name = models.CharField(max_length=255)
	last_name = models.CharField(max_length=255)

# if you uncomment this line, you'll notice that the django shell throws an exception
# because it can't concattenate None to String.
# first_name is apparently None in that instance (but it's not.)
# and last_name is apparently """" in that instance (but again, it's not, in my case it was ""Van Wilder"".

#	def __str__(self):
#		return self.first_name + "" "" + self.last_name

admin.site.register(Person)

class StaffMember(Person):
	works_at = models.CharField(max_length=255)

}}}

== SQL Query ==

The resulting SQL query from the queryset is as follows, but seemed okay:


{{{
>>> StaffMember.objects.all().filter(Q(publications_as_author__belongsTo = p) | Q(publications_as_coauthor__belongsTo = p)).query.as_sql()
('SELECT ""wsdmsite_person"".""id"", ""wsdmsite_person"".""first_name"", ""wsdmsite_person"".""last_name"", ""wsdmsite_staffmember"".""person_ptr_id"", ""wsdmsite_staffmember"".""works_at"" FROM ""wsdmsite_staffmember"" LEFT OUTER JOIN ""wsdmsite_publication_authors"" ON (""wsdmsite_staffmember"".""person_ptr_id"" = ""wsdmsite_publication_authors"".""staffmember_id"") LEFT OUTER JOIN ""wsdmsite_publication"" ON (""wsdmsite_publication_authors"".""publication_id"" = ""wsdmsite_publication"".""id"") LEFT OUTER JOIN ""wsdmsite_publication_belongsTo"" ON (""wsdmsite_publication"".""id"" = ""wsdmsite_publication_belongsTo"".""publication_id"") LEFT OUTER JOIN ""wsdmsite_publication_co_authors"" ON (""wsdmsite_staffmember"".""person_ptr_id"" = ""wsdmsite_publication_co_authors"".""staffmember_id"") LEFT OUTER JOIN ""wsdmsite_publication"" T7 ON (""wsdmsite_publication_co_authors"".""publication_id"" = T7.""id"") LEFT OUTER JOIN ""wsdmsite_publication_belongsTo"" T8 ON (T7.""id"" = T8.""publication_id"") INNER JOIN ""wsdmsite_person"" ON (""wsdmsite_staffmember"".""person_ptr_id"" = ""wsdmsite_person"".""id"") WHERE (""wsdmsite_publication_belongsTo"".""project_id"" = %s  OR T8.""project_id"" = %s )', (1, 1))
>>>
}}}

== Notes ==

If I remove any of the two Q functions and the OR relationship, it works perfectly as you would expect it:


{{{
>>> p = Project.objects.get(pk=1)

>>> StaffMember.objects.all().filter(Q(publications_as_author__belongsTo = p))
[<StaffMember: StaffMember object>]
>>> StaffMember.objects.all().filter(Q(publications_as_author__belongsTo = p))[0].first_name
u'Kevin'

>>> StaffMember.objects.all().filter(Q(publications_as_coauthor__belongsTo = p))
[<StaffMember: StaffMember object>]
>>> StaffMember.objects.all().filter(Q(publications_as_coauthor__belongsTo = p))[0].first_name
u'Sven'
}}}


So i would guess it has something to do with the OR relationship."		closed	Database layer (models, ORM)	dev		worksforme	"Q, ""multi-table inheritance"""		Accepted	0	0	0	0	0	0