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
14866	select_related create multiple copies of the same object	madewulf	nobody	"I am not sure this is a bug, it is more a surprising ""feature"" of the ORM, that is probably costing a lot of memory. 

When using select_related on a query, the objects created because of their existence mentioned in select_related can be created multiple times if they are referred by many foreign keys. 

I think this is still unclear, so here is an example : 

Let say we have a model Order and Client


{{{
class Client(models.Model):
    #here fields

class Order(models.Model):
    #... here fields
    client = models.ForeignKey(Client)
}}}


If you execute the following code :



{{{
orders = Order.objects.all()
for order in orders:
    print ""db id: "" , order.client.id, ""object id : "" , id(order.client)
}}}

You will get multiple different object ids for a given db id if there are multiple orders referencing the same client. 

This could easily be avoided, imho, by using a dict storing the db ids for which an object has already been created. 

I do not see use cases where the current behaviour would be better, but I may be mistaken, and I clearly could be missing impacts on aggregation fuctions, or other parts of the ORM. 







"		closed	Database layer (models, ORM)	1.2		duplicate	select_related		Unreviewed	0	0	0	0	0	0