On May 1, 2008, at 11:49 AM, [EMAIL PROTECTED] wrote:
>
>> Now that QSRF has landed, this type of thinking leads me to: who's
>> working on 121-rewrite?
>
> I'm fairly certain that in refactoring QuerySet, OneToOneField has
> been fixed. It's the base mechanism that allows multi-table
> subclassing to work, in fact.
I do not believe you understood what I mean by fixed. OneToOneField
has always worked, halfway. What it doesn't do is follow the
relationship in both directions:
from django.db import models
class A(models.Model):
a1 = models.CharField(max_length=20)
class B(models.Model):
b1 = models.CharField(max_length=20)
b2 = models.OneToOneField(A)
B.objects.select_related() creates this query (MySQL, taken from the
logs):
SELECT `t1_b`.`id`, `t1_b`.`b1`, `t1_b`.`b2_id`, `t1_a`.`id`,
`t1_a`.`a1` FROM `t1_b` INNER JOIN `t1_a` ON (`t1_b`.`b2_id` =
`t1_a`.`id`)
A.objects.select_related() creates this query:
SELECT `t1_a`.`id`, `t1_a`.`a1` FROM `t1_a`
A complete OneToOneField would generate effectively the same query in
both directions, since it's a special type of ForeignKey that the
reverse relationship makes sense to automatically select on.
If this worked, then in the User case, you could select_related() on
the UserProfile, *OR* .select_related() on the User(), and you would
get the same data either way, no matter how many models were connected
via OneToOneField in this manner. I would assume that all the
normal .select_related(***) options would work as well across this,
like "depth" and the new options for picking a subset of fields only
to follow the relations on.
(As an aside, forward FKs on both sides of the OneToOne should be
followed, but that I would assume is an incidental of getting
OneToOnes working this way in the first place).
Does that make more sense as to why it would alleviate the issue?
Thanks,
gav
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