Re: .filter() and .exclude() don't add up

On Mon, Jul 29, 2013, akaariai <akaariai@gmail.com> wrote:

>> I understood that part. But by "more general" I mean one that will work
>> for any case, without having to know where the Nulls might be.
>>
>> So given queryset A, and its subset queryset B, we can place B against A
>> and obtain its complement.
>>
>> Or to put it another way: give me all the items in A that are not in B.
>>
>
>You can do this with a subquery in Django. non_red_things =
>queryset.exclude(pk__in=red_things). If this performs well is a different
>thing.

It seems to take about twice as long to execute, so no, it doesn't perform very well.

>I think that in SQL one can use WHERE (original_condition) is not true;
>which will match both unknown (null comparison's result) and false in the
>original condition.

But this isn't available as a Django query, without using raw SQL?

Daniele

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