many-to-many queryset question

[Carsten Fuchs]

Hi all,

looking at the example models Author and Entry at
https://docs.djangoproject.com/en/1.3/topics/db/queries/, I would like
to run a query like this:

SetOfAuthors = Authors.objects.filter(...)
qs = Entry.objects.filter(authors__in=SetOfAuthors)

such that (pseudo-code):

for e in qs:
"e.authors is a subset of (or equal to) SetOfAuthors"

However, when I try it, the true result seems to be an intersection:

for e in qs:
"There is (at least one) an author in e.authors that is also in
SetOfAuthors"

How do I have to phrase the query in order to obtain only entries whose
authors are all in SetOfAuthors?

Best regards,
Carsten

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[Felipe Morales]

could you possibly show the query generated?... 

# print qs.query

2011/12/6 Carsten Fuchs <carste...@cafu.de>

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[Peter of the Norse]

One possibility is to try two excludes.

bad_authors = Authors.objects.exclude(pk__in=SetOfAuthors)

qs = Entry.objects.exclude(authors__in=bad_authors)

This will return all entries that don't have authors in SetOfAuthors. It might even be easier, if you can skip creating SetOfAuthors in the first place.

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Peter of the Norse

Rahm...@Radio1190.org

[Carsten Fuchs]

Hi Peter,

Am 2012-01-07 03:40, schrieb Peter of the Norse:
> One possibility is to try two excludes.
>
> bad_authors = Authors.objects.exclude(pk__in=SetOfAuthors)
> qs = Entry.objects.exclude(authors__in=bad_authors)
>
> This will return all entries that don't have authors in SetOfAuthors. It might even be
> easier, if you can skip creating SetOfAuthors in the first place.

That works very well! :-)
Thank you very much for your help!