django-rest-frameworkdjango-pagination

Why does my CursorPagination class always return the same previous link?

Trying to paginate a large queryset so I can return to the same position I was in previously even if data has been added to the database.

Currently I have as my pagination class:

from rest_framework.pagination import CursorPagination

class MessageCursorPagination(CursorPagination):
    page_size = 25
    ordering = '-date'

In my View I have:

from rest_framework.generics import GenericAPIView
from rest_framework.authentication import TokenAuthentication, BasicAuthentication

class MessageViewSet(GenericAPIView):
    permission_classes = (IsAuthenticated, )
    authentication_classes = (TokenAuthentication,)
    pagination_class = pagination.MessageCursorPagination
    serializer_class = serializers.MessageSerializer

    def get(self, request, **kwargs):
        account_id = kwargs.get('account_id', None)
        messages = models.Message.objects.filter(
                account=account_id)

        paginated_messages = self.paginate_queryset(messages)
        results = self.serializer_class(paginated_messages, many=True).data
        response = self.get_paginated_response(results)
        return response

While testing to see if I'd set it up right, I got the results I was expecting with a next link and a null for the previous link. After going to the next link I get a new next link, the next set of results, and a previous link. When I continue to the next link I get the same previous link as before, but with the next, next link and the next set of data. No matter how many times I go to the next, next link the previous link remains the same.

Why doesn't the previous link update?

-- Update --

It looks like the cause to my issue is that I have a lot of messages on the same date. Ordering by date it tries to step back to the date before the current cursor. How can I order by date but step through the list using the cursor pagination like I would with ids?

Solution

  • I ended up creating a property on the model that was the date followed by the id of the model.

    I then did an order by on that property and it fixed the issue.

    From the Documentation

    Proper usage of cursor pagination should have an ordering field that satisfies the following: