Thank you Nicolas,
This works:
reg = p.groupregistration_set.all().select_related('group')
name = reg[0].group.name
This also works:
name = p.groupregistration_set.all().select_related('group')[0].group.name
1) Is there any difference? Which one is beter.
2) reg = p.groupregistration_set.all().select_related('group')
name = reg[0].group.name
does second line result in db hit???
3) name =
p.groupregistration_set.all().select_related('group')[0].group.name
this is 1 or 2 hit??
and an optional 10 points question:
4) If I had two members of reg list, how to modify the code above?
Thanks again..
--
--
On Thursday, March 7, 2013 6:35:14 PM UTC+2, Nikolas Stevenson-Molnar wrote:
>
> The biggest hit is probably going to be the reg.group call. You can
> optimize that by using select_related (), which will take what is
> currently 1 + (number of group registrations for the user) queries and
> turn it into 2 queries:
>
> reg = p.groupregistration_set.all().select_related('group')
>
> More on select_related:
> https://docs.djangoproject.com/en/dev/ref/models/querysets/#select-related
>
> _Nik
>
> On 3/6/2013 11:18 PM, Fatih Tiryakioglu wrote:
> > Hi all,
> >
> > Is there any shortcut (minimum db hit) for the following querysets:
> >
> > p = Person.objects.get(mail="[email protected] <javascript:>")
> > p.password & form.password comparison and it is ok.
> >
> > #reversing to the person's groupregisteration, for example:
> > reg = p.groupregistration_set.all() #groupregistratin model is simply
> > person (foreign key) and group (foreign key)
> >
> > #evaluating group of reg list.
> > g = reg.group (for the every member of reg list)
> >
> > #and finally group name
> > n = g.name (for the every member of g list)
> >
> > Which queryset or querysets hits the db, and how can I minimize it.
> >
> >
> >
> > Thanks.
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