hello all!
I have similar problem:
assume books-tabls, in manyToMany relation with tags-table through
bookTagMatch-table
I am looking for a way to do this through the admin filter:
subclass relatedFilter to interpret the url: /?bookTag=7&bookTag=3
and returns book tuples that are tagged under class 7 AND also tagged
under class 3
which equal to books.object.all().filter(tag=3).filter(tag=7)
I search over 'QuerySet API reference' for maybe another url syntax
for it, but failed to... what am I missing?
does anyone know how?
thanks!
tom
On 28 אפריל, 19:37, Tom Evans <tevans...@googlemail.com> wrote:
> On Wed, Apr 28, 2010 at 5:12 PM, HWM-Rocker <olafgla...@gmail.com> wrote:
>
> > On Apr 28, 4:21 am, Tom Evans <tevans...@googlemail.com> wrote:
> >> On Wed, Apr 28, 2010 at 1:00 AM, HWM-Rocker <olafgla...@gmail.com> wrote:
> >> > I have a TaggedObject that has a GenericRelation to Foo with the name
> >> > tags. When I am searching something like that
>
> >> > TaggedObject.objects.filter(Q(tags__tag=1)&Q(tags__tag=4))
>
> >> > I get no Objects in return. But when Ifilterwith (or) '|' then I get
> >> > 4 Objects. But I have only 3 objects tagged. So the object, that was
> >> > tagged with 1 and with 4 will be returnedtwice?
>
> >> > Thats strange. Any idea how to create this queries correctly?
>
> >> > thanks in advance!!!
>
> >> That query looks for tags which are both 1 and 4 at thesametime.
> >> What you want to do is look for tags which are 1, look for tags which
> >> are 4, and intersect them.
>
> >> In other words:
>
> >> TaggedObject.objects.filter(tags__tag=1).filter(tags__tag=4)
>
> > yeah I changed my code, but is there any possibility to do this with
> > Q, so that I can just execute one query in the end? I want to build a
> > complex nested search/filterand Q gives me the possibility to negate
> > queries. Is there a possibility to split those two Q's to behave in a
> > way that would be useful for my case.
>
> >> Cheers
>
> >> Tom
>
> > thx for your tip !!
>
> What you ask the ORM for has more effect on how many queries are done
> than how many times you callfilter() - querysets are only evaluated
> (go to the DB) when they are displayed/iterated through.
>
> This ORM statement:
> TaggedObject.objects.filter(tags__tag=1).filter(tags__tag=4)
>
> would boil down to one SQL statement, joining to the tags tabletwice.
>
> Use the django debug toolbar, or manually examine
> django.db.connection.queries ("from django.db import connection; print
> connection.queries") to see more clearly what the ORM is doing.
>
> In this case you are asking for how you can dynamicallyfilterby tags
> (in an AND search):
>
> qs = TaggedObjects.objects.filter( .. )
> for tag in tag:
> qs = qs.filter(tags__tag=tag)
>
> If you wanted tofilteron (tag a or tag b) and tag c:
> qs = qs.filter(Q(tags__tag=taga) | Q(tags__tag=tagb)).filter(tags__tag=tagc)
>
> I'll leave it up to you to turn that into something dynamic :P
>
> Be aware, each tag you 'AND'filteron adds another join - the joys of RDBMS
>
> Cheers
>
> Tom
>
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