custom pagination of limit and page in Django Rest Framework

Question

I wanted to create custom paginations for this get_queryset.

get_queryset = Comments.objects.filter(language_post_id=post_in_lang_id,is_post_comment=True).order_by('-created_on')[offset:offset+limit]

I want to change the offset value whenever the page_no updates. Suppose someone enters page_no=1, so offset must be 0, and when enters 2, so offset should be 10, and so on. Every time page_no updates, it should update the offset value accordingly.

• like ?page_no=3:

get_queryset = Comments.objects.filter(language_post_id=post_in_lang_id,is_post_comment=True).order_by('-created_on')[offset:offset+limit] # [ 20 : 20 + 10 ]

Answer 1

I guess you want to do that in a ListAPIView. If that's the case, you can do this really simply using PageNumberPagination.
Just define the page size and the page_query_param you want, and the default paginate_queryset() method will take care of everything for you, you don't have to override it or calculate the offset by yourself.

# pagination.py
from rest_framework.pagination import PageNumberPagination

class CustomPagination(PageNumberPagination):
    # Returns 10 elements per page, and the page query param is named "page_no"
    page_size = 10
    page_query_param = 'page_no'


# views.py
from rest_framework.generics import ListAPIView
from my_app.pagination import CustomPagination

class MyListView(ListAPIView):
    pagination_class = CustomPagination
    serializer_class = CommentSerializer
    
    def get_queryset(self): 
        post_in_lang_id = '1'  # Retrieve your post_in_lang_id here
        return Comments.objects.filter(language_post_id=post_in_lang_id,is_post_comment=True).order_by('-created_on')

You can also set it as the default paginator by defining DEFAULT_PAGINATION_CLASS in your settings file.

Here is a mock of what you would get as a result for the first page using this method :

{
    "count": 20,
    "previous": null,
    "next": "http://localhost:8000/api/comments/?page_no=2",
    "results": [  # List of first 10 elements
        {
            "id": 1,
            [...]
        },
        [...]
        {
            "id": 10,
            [...]
        },
    ]
}