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
34198	Django content type prefetching wrong data	Mahavir Agrawal	Mahavir Agrawal	"
{{{
class Base1(models.Model): 
    value = models.CharField(max_length=20) 
 
 
class Base2(models.Model): 
    value = models.CharField(max_length=20) 
 
 
class LinkedWithBase1(models.Model): 
    f = models.ForeignKey(Foreign, on_delete=models.PROTECT, related_name=""a_objects"") 
 
 
class LinkedWithBase2(models.Model): 
    f = models.ForeignKey(OtherForeign, on_delete=models.PROTECT, related_name=""b_objects"") 
 
 
class Connection(models.Model): 
    ct = models.ForeignKey(ContentType, on_delete=models.PROTECT) 
    object_id = models.IntegerField() 
    object = GenericForeignKey(ct_field='ct', fk_field='object_id') 
}}}

**The data presentation :-** 

1) Base1 Model

|| id || value||
|| 1||  Foreign||

2) Base2 Model

|| id || value||
|| 1||  OtherForeign||

3) LinkedWithBase1 model 
|| id || f_id (FK)||
|| 1||  1||

4) LinkedWithBase2 model 
|| id || f_id (FK)||
|| 1||  1||

Let's assume **LinkedWithBase1** model content_type id is **1** and **LinkedWithBase2** content_type  id is **2**.

Connection model
|| id || ct_id || object_id ||
|| 1 ||  1 ||  1||
|| 2 ||  2 ||  1||

**1 row is connected with id  1 of LinkedWithBase1 model 
2 row is connected with  id 1 of  LinkedWithBase2 model**

When i was run below code 

{{{
connections = Connection.objects.prefetch_related(""object__f"").all()

for i in connections:
    print(i.object.f.value)  
}}}


**Actual Output**
Foreign  
Foreign

**Expected Output**
Foreign
OtherForeign

In 1st iteration **i.object.f** evaluate **Base1 model instance** which is right
In 2nd iteration **i.object.f** it should be take **Base2 model instance** but django takes as **Base1 model instance** 
because of wrong prefetching occurs

But when i removed  **f** from prefetch_related  it gives me a expected result 

Ex: connections = Connection.objects.prefetch_related(""object"").all()

i am very confident prefetching went wrong because i spent 5 hours to debug this issue in Django core and i got it doing wrong prefetching when it has a multiple content types as same name of key like **f** attribute in above code, I have patch for this.

I will very greatful if you give me a chance to fix this issue
"	Bug	closed	Database layer (models, ORM)	4.1	Normal	duplicate			Unreviewed	0	0	0	0	0	0