[Fixed]-Django queryset subset with custom manager?

by

1👍

You can do it in many ways. Some of them:

  • Make all calculation in the view and pass to the context prepared data:

    customers = Customer.objects.filter(name="foo")
active_customers_count = customers.filter(is_active=True)

  • Custom template tag (docs):

    tag

    from django import template

register = template.Library()


@register.assignment_tag
def filter_qs(qs, **kwargs):
    return qs.filter(**kwargs)

    template

    {% filter_qs customers is_active=True as active_customers %}
{{ active_customers|length }}

  • Custom Manager with custom QuerySet (docs):

    models

    class IsActiveQuerySet(models.QuerySet):
    def active(self):
        return self.filter(is_active=True)


class IsActiveManager(models.Manager):
    def get_queryset(self):
        return IsActiveQuerySet(self.model, using=self._db)


class Customer(BaseInfo):
   objects = IsActiveManager()
   name = models.CharField(max_length=50)

    template

    {{ customers.active|length }}

I would strongly recommend you to go with the first option, it will be the most “Pythonic” way.
Anyway django will make 2 separate sql queries for any of solution listed above.

👤crash843

Leave a comment