Django权限未得到缓存

Question

我在django视图中使用带有@permission_required装饰器的django 1.11，postgres。问题是，对于任何视图，我都会得到2个额外的SQL查询-

1）SELECT ••• FROM "auth_permission" INNER JOIN "account_myuser_user_permissions" ON ...

2）SELECT ••• FROM "auth_permission" INNER JOIN "auth_group_permissions" ON ...

Django文档指出- The ModelBackend caches permissions on the user object after the first time they need to be fetched for a permissions check.

我不明白为什么第一次不缓存权限，或者我丢失了什么？