id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
31767	QuerySet.none() on combined queries returns all results.	Tom Carrick	Mariusz Felisiak	"I came across this issue on Stack Overflow. I'm not 100% sure it's a bug, but it does seem strange. With this code (excuse the bizarre example filtering):

{{{
class Publication(models.Model):
    pass

class Article(models.Model):
    publications = models.ManyToManyField(to=Publication, blank=True, null=True)

class ArticleForm(forms.ModelForm):
    publications = forms.ModelMultipleChoiceField(
        Publication.objects.filter(id__lt=2) | Publication.objects.filter(id__gt=5),
        required=False,
    )

    class Meta:
        model = Article
        fields = [""publications""]

class ArticleAdmin(admin.ModelAdmin):
    form = ArticleForm
}}}

This works well. However, changing the `ModelMultipleChoiceField` queryset to use `union()` breaks things.

{{{
publications = forms.ModelMultipleChoiceField(
    Publication.objects.filter(id__lt=2).union(
        Publication.objects.filter(id__gt=5)
    ),
    required=False,
)
}}}

The form correctly shows only the matching objects. However, if you submit this form while empty (i.e. you didn't select any publications), ALL objects matching the queryset will be added. Using the `OR` query, NO objects are added, as I'd expect."	Bug	closed	Database layer (models, ORM)	dev	Normal	fixed			Accepted	1	0	0	0	0	0