Optimizing foreign key & manytomany field in REST API query - rest

Question

I'm wondering is there anyway to optimize an api when using foreign key and ManytoMany field, for example :
Serializer :
class SerializerA(serializers.ModelSerializer):
class Meta:
model = Model_A
fields = ('id', 'official_name', 'gender')
depth = 1
class SerializerB(serializers.ModelSerializer):
user = SerializerA(many=True)
class Meta:
model = Model_B
fields = ('id', 'project_name','project_type', 'project_start_date', 'user')
depth = 1
API :
class ReportAPI(APIView):
def get(self, request):
all_projects = Model_B.objects.all()
project_serializer = SerializerB(all_projects, many=True)
return Response(project_serializer.data)
now with this, if i go to the API url, and debug this page, it''l show that I'm querying 78 times from the SQL query. But if I remove one field from manytoMany seriealizer field which the 'gender', the page now will only query from the database 21 times, so my question is again, how can I optimize this?

Answer 1

You can use select_related (for ForeignKey) and/or prefetch_related (For ManyToMany or ManyToOne) so that it will not hit the database for each Model_B object.
If user is a FK in Model_B then you can do:
class ReportAPI(APIView):
def get(self, request):
all_projects = Model_B.objects.all().select_related('user')
project_serializer = SerializerB(all_projects, many=True)
return Response(project_serializer.data)
If the user model has other FK that you need in it's serializer, then you can also do select_related('user', 'user__other_field').