Thank you for answering and for the workaround tip.
I agree, exclude should be the complement of filter. This did not work
in 0.96 but works now, which is great.
I don't think however that it is a good idea to let filter(~Q()) mean
'not exists', i.e. be equivalent to 'exclude', for multi valued
relations, while it means 'not' in other cases.
It would be nice if ~Q also for these relations could mean 'not',
which is sometimes needed (as is 'and', 'or' and parenthesis) when
creating expressions.
In my opinion if Entry.objects.filter(~Q(condition)) gives a set of
entries then Blog.objects.filter(~Q(entry__condition)) should give the
blogs of these entries, while
Blog.objects.exclude(~Q(entry__condition)) should give the
complementary blogs, just as the case is without the ~ characters.
Regards,
Göran
On Jul 17, 6:49 pm, Malcolm Tredinnick <[EMAIL PROTECTED]>
wrote:
> On Thu, 2008-07-17 at 02:39 -0700, Göran Åström wrote:
> > In my view the 'not' can be interpreted differently.
> > Look at the following requests:
>
> > 1. Give me blogs with entries matching a criteria.
> > 2. Give me blogs with entries not matching a criteria.
> > 3. Give me blogs without entries matching a criteria.
>
> Whilst alternate interpretations are always possible, interpreting
> exclude as the complement of include ("filter") is the most natural. So
> excluding based on a particular entry means to take the whole set of
> blogs and remove those containing an entry that matches the condition
> (since the filter() version would be those blogs containing an entry
> that match the condition). Thus exclude() and filter() are opposites.
>
> Since (a) writing your own Q-like object is possible and not
> particularly hard and (b) nested queries are more or less supported (the
> API doesn't exist, but all the under-the-cover implementation is there
> and it's possible to use it if you read the code), your second option
> has at least two ways to be accessed. So keeping the most natural
> version of exclude() that we have now still seems like the best option
> to me. That way, nothing is impossible and the obvious usage is the
> right one.
>
> Regards,
> Malcolm
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