小记， django select 字段中含有连表查询 分页优化

• 例如 查询每本书的借阅数量，在 select 中加入连表

select id,(select count(*) from book where book.user_id= user.id) as count,name from user; 

• 在 django 分页最后会变成

  select count(*) from ( select id,(select count(*) from book where book.user_id= user.id) as count,name from user) 

• 优化,在 restframework 中分页, 去掉 select 字段 ，只保留 filter 条件

  from rest_framework.pagination import PageNumberPagination from django.core.paginator import Paginator from django.utils.functional import cached_property class Pagination(Paginator): @cached_property def count(self): """Return the total number of objects, across all pages.""" c = getattr(self.object_list, 'count', None) if callable(c) and not inspect.isbuiltin(c) and method_has_no_args(c): return self.object_list.values('id').count() return len(self.object_list) class CustomPagination(PageNumberPagination): django_paginator_class = TicketPagination 

• 接口中使用

  class API(ModelViewSet): pagination_class = CustomPagination