Ah - ok, cool, good to know. I am on 1.1 pre-alpha SVN-9814. Am
moving soon to the 1.1. beta. I originally encountered this on a case
that wasn't quite what I posted. I had a situation where I was
guaranteed that my Task had only a single tile in the tiles field. So
I was trying to filter like this:
PdTask.objects.filter(tiles__in=pdTask.objects.all()[0])
IE, I was trying to find all PdTasks that contained a tile that was
the same as the single tile in pdTask. Then I started experimenting
and began to think that maybe I just didn't understand the manytomany
queries at all - thought maybe I was doing it wrong.
Anyway, your answer allayed my concerns - I have a workaround, no
problem there, just didn't want to find that I was using the queries
wrong in general.
Malcolm - monitoring this group must be a full time job for you.
Thank you so much for all of your responses.
Margie
On Apr 15, 11:39 pm, Malcolm Tredinnick <malc...@pointy-stick.com>
wrote:
> On Wed, 2009-04-15 at 23:13 -0700, Margie wrote:
>
> [...]
>
> > # PROBLEM IS HERE
> > # Find all pdtasks that have an entry in tiles that is in slice 0:4 of
> > Tile.objects.all()
> > # I think this should return bar as well, but it returns an empty
> > list. WHY???
> > (Pdb) PdTask.objects.filter(tiles__in=Tile.objects.all()[0:4])
> > []
>
> Are you using Django 1.0.X here? Because nested queryset support only
> exists in 1.1-beta and later. Tile.objects.all()[0:4] is a queryset in
> that expression and so won't make sense as an rvalue in 1.0.X.
>
> If you are using 1.0.X, you could write that as:
>
> values = Tile.objects.values_list("id", flat=True)[0:4]
> PdTask.objects.filter(tiles__in=values)
>
> or you could use the slightly ugly hack involving ".query" described in
> [1]
>
> [1]http://docs.djangoproject.com/en/dev/ref/models/querysets/#in
>
> Also, I hope your Tasks model has a Meta.ordering specification,
> otherwise you could well start seeing all sorts of unexpected (but
> completely correct) results when using slices. Database servers are not
> required to serve up results in any particular order (or even the same
> order on successive queries) unless you specify an ordering.
>
> Regards,
> Malcolm
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com
To unsubscribe from this group, send email to
django-users+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~----------~----~----~----~------~----~------~--~---
