Django ; exclure devant annoter exclut trop - Stack Overflow

I have two models

class Foo(models.Model):
    pass

class Bar(models.Model):
    foo = models.ForeignKey(Foo)
    state = models.CharField()

I would like to count all of the Bars grouped by Foo. This is accomplished by:

Foo.objects.annotate(num_bars=Count('bar'))

Which gives me back a QuerySet of Foos annotated with the number of Bars.

Now I would like to exclude some Bars based on their state. Let's say the states are all either 'A' or 'B' and I don't want to count the 'B's. I tried the following:

Foo.objects.exclude(bar__state='B').annotate(num_bars=Count('bar'))

But this returns a count of zero for any Foo where there is at least one Bar with state 'B'. I thought it would have returned the same as:

Foo.objects.filter(bar__state='A').annotate(num_bars=Count('bar'))

Which, in this case also excludes all 'B'. Unfortunately, the method using filter isn't so good because there are actually several states and I only want to exclude one (and in principle, there could be more in the future).

So, what am I doing wrong? What is the right way to exclude before doing an annotation?

I have two models

class Foo(models.Model):
    pass

class Bar(models.Model):
    foo = models.ForeignKey(Foo)
    state = models.CharField()

I would like to count all of the Bars grouped by Foo. This is accomplished by:

Foo.objects.annotate(num_bars=Count('bar'))

Which gives me back a QuerySet of Foos annotated with the number of Bars.

Now I would like to exclude some Bars based on their state. Let's say the states are all either 'A' or 'B' and I don't want to count the 'B's. I tried the following:

Foo.objects.exclude(bar__state='B').annotate(num_bars=Count('bar'))

But this returns a count of zero for any Foo where there is at least one Bar with state 'B'. I thought it would have returned the same as:

Foo.objects.filter(bar__state='A').annotate(num_bars=Count('bar'))

Which, in this case also excludes all 'B'. Unfortunately, the method using filter isn't so good because there are actually several states and I only want to exclude one (and in principle, there could be more in the future).

So, what am I doing wrong? What is the right way to exclude before doing an annotation?

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