On Tuesday 22 January 2008 16:16:34 code_berzerker wrote:
> theres line of code in tutorial:
>
> Poll.objects.all().order_by('-pub_date')[:5]
>
> this gives 5 Poll objects. I wonder if this is efficient way of
> getting them? Does django get all rows first and then sort it and then
> slice it to get only 5? Or is it optimized somehow. The question is if
> its simplified for the tutorial and inefficient or this is the right
> way to do it?
this is the right way..
qs = Poll.objects.all().order_by('-pub_date')[:5]
qs now is only 'queryset', and real query into database happen when you
iterating objetcs
e.g.
for poll in qs:
do_something_with(i)
or
{% for poll in polls %}...{% endfor %}
all this calls (order_by,filter...) only affects future query
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