DRF Custom Pagination not working properly

Question

Recently I was working with drf pagination class,PageNumberPagination.I may or may not have encountered a weird bug . The official docs mention,to overide the page size of PageNumberPagination we have to create a Custom paginator which overides the page size configuration like shown below

class StandardResultsSetPagination(PageNumberPagination):
    page_size = 100
    page_size_query_param = 'page_size'
    max_page_size = 1000
class BillingRecordsView(generics.ListAPIView):
    queryset = Billing.objects.all()
    serializer_class = BillingRecordsSerializer
    pagination_class = LargeResultsSetPagination

But when I tried to do the same the custom paginator was using the default setting as 100 Here's my snippet I used

class StandardResultsSetPagination(PageNumberPagination):
    page_size = 10
    page_size_query_param = 'page_size'
    max_page_size = 100

class TrendingClassesView(ListAPIView):
    pagination_class = StandardResultsSetPagination
    serializer_class = BaseClassTileSerializer
    queryset = BaseClass.objects.all()

One moment the code the working fine but after playing around with the page size for some time the paginator just stopped working, I have to do something like below to make the page size working

class StandardResultsSetPagination(PageNumberPagination):
    page_size = 10
    page_size_query_param = 'page_size'
    max_page_size = 100

    def get_page_size(self, request):
        return 10

This is my rest framework settings

REST_FRAMEWORK = {
    'UPLOADED_FILES_USE_URL':
    True,
    'DEFAULT_PARSER_CLASSES': [
        'rest_framework.parsers.JSONParser',
        'rest_framework.parsers.MultiPartParser',
        'rest_framework.parsers.FileUploadParser',
        'rest_framework.parsers.FormParser',
    ],
    "TIME_FORMAT":
    "%I:%M %p",
    "TIME_INPUT_FORMATS": ["%I:%M %p", "%H:%M"],
}

I guess I may be doing something wrong but I am not able to find the mistake.

score 1 · Accepted Answer · answered Mar 29 '21 at 04:45

Yeah,this was probably dumb but anyways I figured out the issue .The problem wasn't with the given two views so I didn't provide proper info here.After writing the above comment I started looking for if I am overiding the page size somewhere else So I found this

class FocusView(ListAPIView):
    authentication_classes = (JWTAuthentication, TokenAuthentication,
                              SessionAuthentication, BasicAuthentication)
    permission_classes = (IsAuthenticated, IsCustomer, )
    renderer_classes = (
        JSONRenderer,
       
    )
    pagination_class = StandardResultsSetPagination
    serializer_class = FocusTileSerializer
    pagination_class.page_size=100 #this line was the culprit here

This view for just below the view I used above , so when the server reload python loads all the modules and files so this view was overiding the page_size of the Custom paginator.I don't really know if it is even supposed to do that,but it surely should be mentioned in docs or maybe I missed it.

score 0 · Answer 2 · answered Mar 28 '21 at 17:49

I don't see any mistake in custom pagination, although you do not have to override the get method. Try setting default pagination class in settings.

REST_FRAMEWORK = {
    'UPLOADED_FILES_USE_URL':
    True,
    'DEFAULT_PARSER_CLASSES': [
        'rest_framework.parsers.JSONParser',
        'rest_framework.parsers.MultiPartParser',
        'rest_framework.parsers.FileUploadParser',
        'rest_framework.parsers.FormParser',
    ],
    "TIME_FORMAT":
    "%I:%M %p",
    "TIME_INPUT_FORMATS": ["%I:%M %p", "%H:%M"],
    'DEFAULT_PAGINATION_CLASS': 'your.path.StandardResultsSetPagination'
}

It's mentioned in the documentation too : DRF pagination

PS: Please check the queryset and viewset too, it's possible that the bug might be from the query you are fetching the results.

Yeah maybe that will work but I am literally thinking why the given thing isn't working, moreover when i tried to print self.page_size in the get method, it was printing 100,as if the fn is defying the laws of inheritance itself. — Kunal Solanke, Mar 29 '21 at 04:23
Haha great that you found the bug! :) I would suggest you set a default in settings and override them later — Neeraj, Mar 29 '21 at 09:31

DRF Custom Pagination not working properly

2 Answers2