Question

对我来说这有点令人费解，所以我决定寻求帮助。

我所拥有的是一个标准用户模型和一个表格，用于跟踪用户是否互相跟随from_user，to_user和following值。第一个是我的用户表的外键，第三个是布尔值。

我想要做的是能够覆盖django admin中的默认get_queryset方法，以便根据用户拥有的关注者数量进行排序。

我目前被困的地方实际上是在注释追随者的数量，这可能是我想念的小事，但是这里是我的代码：

def get_queryset(self, request):
    return AuthUser.objects.annotate(
        followers_count=Sum(
            Case(
                When(user_relations__from_user=1, user_relations__to_relation__following=True, then=1),
                default=0,
                output_field=IntegerField()
            )
        ))

错误的部分 - 我坚持使用user_relations__from_user=1，这应该是当前正在评估的用户的身份。

我在所有条目的聚合中需要做的是我在用户模型中的单个案例场景中已经做过的事情：

@property
def num_followers(self):
    return UserRelations.objects.filter(from_user=self, following=True).count()

看起来很简单，但如何在注释时获得from_user=self？

编辑：尝试使用F user_relations__from_user_id__pk=F('id')

时添加堆栈跟踪

附加说明 - 我的from_user和to_user字段实际上名为from_user_id和to_user_id - 希望这不会导致额外的混淆。对不起。

Internal Server Error: /admin/pkm_user/authuser/
Traceback (most recent call last):
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/contrib/admin/options.py", line 616, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/views/decorators/cache.py", line 57, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/contrib/admin/sites.py", line 233, in inner
    return view(request, *args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/utils/decorators.py", line 34, in _wrapper
    return bound_func(*args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/utils/decorators.py", line 30, in bound_func
    return func.__get__(self, type(self))(*args2, **kwargs2)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/contrib/admin/options.py", line 1548, in changelist_view
    self.list_max_show_all, self.list_editable, self)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/contrib/admin/views/main.py", line 47, in __init__
    self.root_queryset = model_admin.get_queryset(request)
  File "/home/bastor/Work/pokemall-api/django/pkm_user/admin.py", line 65, in get_queryset
    output_field=IntegerField()
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/query.py", line 794, in annotate
    obj.query.add_annotation(annotation, alias, is_summary=False)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 977, in add_annotation
    summarize=is_summary)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/aggregates.py", line 20, in resolve_expression
    c = super(Aggregate, self).resolve_expression(query, allow_joins, reuse, summarize)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/expressions.py", line 491, in resolve_expression
    c.source_expressions[pos] = arg.resolve_expression(query, allow_joins, reuse, summarize, for_save)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/expressions.py", line 779, in resolve_expression
    c.cases[pos] = case.resolve_expression(query, allow_joins, reuse, summarize, for_save)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/expressions.py", line 713, in resolve_expression
    c.condition = c.condition.resolve_expression(query, allow_joins, reuse, summarize, False)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/query_utils.py", line 91, in resolve_expression
    clause, joins = query._add_q(self, reuse, allow_joins=allow_joins, split_subq=False)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1332, in _add_q
    allow_joins=allow_joins, split_subq=split_subq,
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1194, in build_filter
    lookups, value)
  File "/home/bastor/Work/pokemall-api/env/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 1709, in get_lookup_constraint
    raise exceptions.FieldError('Relation fields do not support nested lookups')
FieldError: Relation fields do not support nested lookups

Answer 1

我认为您正在寻找Keep WebSocket alive in Mobile Safari：

from django.db.models import F

def get_queryset(self, request):
    return AuthUser.objects.annotate(
        followers_count=Sum(
            Case(
                When(user_relations__to_relation__from_user__id=F('id'),
                     user_relations__to_relation__following=True, then=1),
                default=0,
                output_field=IntegerField()
            )
        ))

Django条件注释计数与过滤器（多对多）跟随者/下表

1 个答案: