CODEWITHSUNDEEP
djangodjango-models
user1187968
user1187968

Reputation: 7986

Django model - select related count

I have the following model, and I need to find out how many OtherModel instances are pointing to the same MyModel instance. 

class MyModel(models.Model):
    int = models.SmallIntegerField()

class OtherModel(models.Model):
    other_model = models.ForeignKey(MyModel, null=True, blank=True)
    int = models.SmallIntegerField()

I can use a for-loop, but the performance is very bad. Is there any other way I can select all MyModel objects, and get the related count in one query? 

for m in MyModel.objects.all(): 
       count = self.othermodel_set.count()

Upvotes: 5

Views: 2056

Answers (1)

Shang Wang
Shang Wang

Reputation: 25539

from django.db.models import Count

result = MyModel.objects.all().annotate(othermodel_count=Count('othermodel'))

Django doc about aggregation features.

Upvotes: 5

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