Django REST Framework 之基于游标、偏移量的分页

1. 普通分页：看第几页，每页显示多少条数据
2. 基于偏移量分页，在某个位置，向后查看多少条数据(offset limit)
3. 游标分页，加密分页，只能看上一页和下一页，记录当前id的最大值和最小值

from filelibrary_sourcegroup.serializers import user
from rest_framework.response import Response

from rest_framework.pagination import PageNumberPagination
from rest_framework.pagination import LimitOffsetPagination
from rest_framework.pagination import CursorPagination



class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = PageNumberPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)

        return pg.get_paginated_response(ser.data)

重写普通分页，使可配置：

class MyPageNumberPagination(PageNumberPagination):
	# 每页默认数量
    page_size = 2
    # 页码参数
    page_query_param = 'page'
    # 指定最大数量的参数
    page_size_query_param = "page_size"
    # 每页最大数量
    max_page_size = 4


class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = MyPageNumberPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)
		
		# 使用 get_paginated_response 会带有count、next 等参数
        return pg.get_paginated_response(ser.data)

效果：

class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = LimitOffsetPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)

        return pg.get_paginated_response(ser.data)

重写偏移量分页，使可配置：

class MyLimitOffsetPagination(LimitOffsetPagination):
    default_limit = 2
    limit_query_param = 'limit'
    offset_query_param = 'offset'
    max_limit = 4


class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = MyLimitOffsetPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)

        return pg.get_paginated_response(ser.data)

效果：
limit 100 但设置的最大 limit 是 4。

class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = CursorPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)

        return pg.get_paginated_response(ser.data)

重写游标分页，使可配置：

class MyCursorPagination(CursorPagination):
    cursor_query_param = 'cursor'
    page_size = 2
    ordering = 'id'
    page_size_query_param = "page_size"
    max_page_size = 4


class UserInfo(APIView):

    def get(self, request):
        users = ReviewUserInfo.objects.all().order_by("id")
        pg = MyCursorPagination()
        q = pg.paginate_queryset(users, request, self)
        ser = user.UserSerializer(q, many=True)

        return pg.get_paginated_response(ser.data)

效果：

游标分页核心逻辑：
会记录当前id的最大值和最小值，再查询时使用 orm 里面的 gt 和 lt 进行数据库层面的过滤，提高效率。

# If we have a cursor with a fixed position then filter by that.
if current_position is not None:
    order = self.ordering[0]
    is_reversed = order.startswith('-')
    order_attr = order.lstrip('-')

    # Test for: (cursor reversed) XOR (queryset reversed)
    if self.cursor.reverse != is_reversed:
        kwargs = {order_attr + '__lt': current_position}
    else:
        kwargs = {order_attr + '__gt': current_position}

    queryset = queryset.filter(**kwargs)