How to use single nested serializer's data in more than one variable of parent serializer with single db call in DRF?

Question

How can I get or store data of EmployeeSerializer somewhere so that I can use it again for getting active members count instead of making a new database call for getting count of active members?

class ProjectSerailizer(serializers.ModelSerializer):
  members = EmployeeSerializer(many=True)#returns all members of a project
  active_members_count = serializers.SerializerMethodField()# get count of members which are having status active
  class Meta:
    model = Project
    fields = ('id','name','members','active_members_count')
  
  def get_active_members_count(self,obj):
    #How can I omit this extra db call? as i am already having data in members variable from EmployeeSerializer, can i loop over members variable somehow and count the active ones?
    count = obj.members.filter(status='Active').count()
    return count

Answer 1

You can set queryset in your view with select_related() and filtered annotate()

django.db.models import Count, Q

queryset = Project.objects.select_related('members').annotate(
    active_members_count = Count('members', filter=Q(members__status = 'Active'))
)

Then you will get active_members_count and other members fields in ProjectSerailizer without extra database calls