Django Rest Framework filtering a field with null and multiple values

Question

I am using Django Rest Framework and want to filter the queryset in a view based on a certain field name.

The filter values would be null and additionally any other particular value for the field blog_category which is a ForeignKey value. So filter query should be on two query params

class Blog(ListCreateAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_fields = {'blog_category': ['isnull', 'exact', 'in']}

I have added the lookup fields isnull to filter null values

I have tried the following url requests but they do not work

/blog/?blog_catgeory__in=1,null
/blog/?blog_catgeory__in=1,isnull
/blog/?blog_catgeory__in=1,isnull=true
/blog/?blog_catgeory__in=1&blog_category__isnull=true

How do I get this work?

Edit After answer Javohir Elmurodov's answer

I made the following modifications but it still does not work

class NumberInFilter(django_filters.BaseInFilter, django_filters.NumberFilter):
    pass


class BlogFilter(filters.FilterSet):
    blog_category = NumberInFilter(field_name='blog_category', lookup_expr='in')
    blog_category__isnull = BooleanFilter(
        field_name='blog_category', lookup_expr='isnull')


class Blog_ListView(ListData, CreateData, CustomGenericAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_class = BlogFilter

I tried the following links

/blog/?blog_catgeory=1&blog_category__isnull
/blog/?blog_catgeory=1&blog_category__isnull=true

Still does not work

I want to search for all entries in queryset that are null OR a particular value in blog_category

did you try /blog/?blog_catgeory__in=1&blog_category__isnull? — sudden_appearance
– sudden_appearance, Commented Mar 3, 2022 at 12:17
@sudden_appearance Yes I had tried this. It returns only the results with blog_catgeory__in=1 — dracarys
– dracarys, Commented Mar 3, 2022 at 12:26
Do you have any blog_category null Blogs. Is Foreign key null=True — Javohir Elmurodov
– Javohir Elmurodov, Commented Mar 3, 2022 at 13:02
Could you try blog_category__isnull = BooleanFilter( field_name='blog_category', lookup_expr='isnull') to blog_category_isnull = BooleanFilter( field_name='blog_category', lookup_expr='isnull'), because it conflict with autofilter. — Javohir Elmurodov
– Javohir Elmurodov, Commented Mar 4, 2022 at 5:23

Javohir Elmurodov · Accepted Answer · 2022-03-03 13:32:07Z

1

It’s not always appropriate to directly match a filter to its model field’s type, as some lookups expect different types of values. This is a commonly found issue with in, range, and isnull lookups.

While the underlying column type for category is an integer, isnull lookups expect a boolean value.

You can check in Filter and lookup expression mismatch (in, range, isnull)

answered Mar 3, 2022 at 13:32

Javohir Elmurodov

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1 Comment

dracarys Over a year ago

I tried what you proposed, it still does not work. Please see the updated question for the modifications that I made

dracarys · Accepted Answer · 2022-03-03 15:22:58Z

The above problem can be solved by overriding the filter method

from django.db.models import Q
from django_filters import rest_framework as filters
from django_filters import CharFilter

class BlogFilter(filters.FilterSet):
    blog_category = CharFilter(field_name='blog_category_mast',
                               lookup_expr='exact',method='include_null')

    def include_null(self, queryset, name, value):
        return queryset.filter(
            Q(**{f'{name}__isnull': True}) | Q(**{name: value})
        )


class Blog(ListCreateAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_class = BlogFilter

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