On Mon, Aug 3, 2009 at 5:12 AM, Malcolm
Tredinnick<malc...@pointy-stick.com> wrote:
>
> On Mon, 2009-08-03 at 02:48 -0700, alant...@neei.uevora.pt wrote:
>> Hello,
>>
>> I'm displaying lot of user profile picture with are on a user profile
>> (i'm using contrib.auth). So for each picture I have a query for the
>> user profile.
>>
>> I wanted to use User.objects.filter(stuff).select_related
>> ('userprofile') but this has no effect. Any ideas how to prevent the
>> +200 queries from happening?
>
> The link between the two models runs from UserProfile -> User, not the
> other way around. The select_related() call only follows forwards links,
> so it will not traverse from User to UserProfile. It's not completely
> trivial to add backwards-link following, particularly because there can
> be multiple values for backwards links.
>
> However, you can often turn this type of query around. Instead of
> filtering User objects, filter Userprofile objects, where you can use
> select_related(). Thus
>
> User.objects.filter(username="fred")
>
> becomes
>
> UserProfile.objects.filter(user__username="fred").select_related()
>
> The main trick here is that each condition needs the "user__" bit
> prepended, so a little munging of filters -- either automatically or by
> hand -- is required. You can still access the User instance attributes
> via
>
> obj.user.username
>
> where "obj" is now a UserProfile instance.
>
> Regards,
> Malcolm
>
>
> >
>
It's worth noting that the ability to do this is the subject of ticket
7270: http://code.djangoproject.com/ticket/7270
Alex
--
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right to say it." -- Voltaire
"The people's good is the highest law." -- Cicero
"Code can always be simpler than you think, but never as simple as you
want" -- Me
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