Is there a good reason why Django querysets can't be intersected?

[cool-RR]

Hi everyone,

I understand that there's no way to get the intersection of two querysets in Django. Whenever I need to get the intersection of two querysets, I need to refactor my code to get pure Qs for those querysets and intersect those. This can be annoying sometimes.

My question: Is there a good reason why Django querysets can't be intersected? Do you think it should be implemented?

Thanks,

Ram.

[Shawn Milochik]

It seems to work for me:

a = Client.objects.filter(name__istartswith='a')                   b = Client.objects.filter(name__iendswith='t')                                  

print a.count()                                                   print b.count()                                                                                                                 

c = a & b                                                         print c.count() 

[Ram Rachum]

Oh my fucking God I'm an idiot. I distinctly remember it not working. Happy it's working! 

Is it implemented efficiently?

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[Ram Rachum]

Also, is it a recently added feature?

[Shawn Milochik]

I don't know anything about efficiency, but it works at least as far back as Django 1.3. I'd assume that, with lazy evaluation, it's probably about as efficient as anything in the ORM.

[James Bennett]

QuerySets have supported the '&' operator (as measured by implementing the __and__() method) for as long as they've been in Django; the implementation dates all the way back to 0.95.

[Ram Rachum]

Wonderful!

Followup question: Is there any reason why ~ isn't supported? (It's supported on Q, but not QuerySet.)

On Mon, Mar 17, 2014 at 3:17 AM, James Bennett <ubern...@gmail.com> wrote:

QuerySets have supported the '&' operator (as measured by implementing the __and__() method) for as long as they've been in Django; the implementation dates all the way back to 0.95.

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