python - django-filter 乱用空字段

Question

我设置 django-filter过滤我的一些列表。这是其中之一，带有自定义表单:

class BookingListFiltersForm(forms.Form):

    state__in = forms.MultipleChoiceField(
        choices=Booking.STATE_CHOICES, required=False,
        label=_("État"), widget=forms.CheckboxSelectMultiple)
    source__in = forms.ModelMultipleChoiceField(
        queryset=Platform.objects.all(), required=False,
        label=_("Source"), widget=ModelSelect2Multiple(
            url='autocomplete:platform'))


class BookingManagerFilter(filters.FilterSet):

    payments__date = filters.DateFilter(method='payments__date_filter')
    payments__method = filters.ChoiceFilter(
        method='payments__method_filter',
        choices=BookingPayment.METHOD_CHOICES,
    )

    class Meta:
        model = Booking
        fields = {
            'period': [
                'endswith', 'endswith__gte', 'endswith__lte',
                'startswith', 'startswith__gte', 'startswith__lte',
            ],
            'state': ['in'],
            'source': ['in'],
            'booking_date': ['date', 'date__lte', 'date__gte'],
            'accommodation': ['in'],
            'guest': ['exact']
        }

    def get_form_class(self):
        return BookingListFiltersForm

    def payments__date_filter(self, queryset, name, value):
        return queryset.filter(**{name: value})

    def payments__method_filter(self, queryset, name, value):
        return queryset.filter(**{name: value})

表单是通过 GET 方法提交的。当字段“source__in”为空时，查询字符串类似于“?state__in=1”。在这种情况下，我的页面中没有结果(这出乎意料，如果未填写字段，我希望结果不会根据该字段进行过滤)。

我查看了调试工具栏以获取有关已执行 SQL 查询的更多信息。令人惊讶的是，我没有找到相关查询集的 SQL 查询! (而如果 querystring 是 "?state__in=1&source__in=2"，结果是预期的，我可以在调试工具栏中找到相关查询)

所以我尝试使用 print(str(filters.qs.query)) 来强制印象 SQL 查询。新惊喜，这触发了 EmptyResultSet 异常:

Traceback:

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  35.             response = get_response(request)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  128.                 response = self.process_exception_by_middleware(e, request)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/views/generic/base.py" in view
  69.             return self.dispatch(request, *args, **kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/utils/decorators.py" in _wrapper
  62.             return bound_func(*args, **kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/contrib/auth/decorators.py" in _wrapped_view
  21.                 return view_func(request, *args, **kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/utils/decorators.py" in bound_func
  58.                 return func.__get__(self, type(self))(*args2, **kwargs2)

File "/home/tony/Workspace/cocoonr/utils/views/manager.py" in dispatch
  29.         return super().dispatch(*args, **kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/views/generic/base.py" in dispatch
  89.         return handler(request, *args, **kwargs)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/views/generic/list.py" in get
  142.         self.object_list = self.get_queryset()

File "/home/tony/Workspace/cocoonr/booking/views/manager.py" in get_queryset
  73.         queryset = super().get_queryset()

File "/home/tony/Workspace/cocoonr/utils/views/common.py" in get_queryset
  118.         print(self.filters.qs.query)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/db/models/sql/query.py" in __str__
  252.         sql, params = self.sql_with_params()

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/db/models/sql/query.py" in sql_with_params
  260.         return self.get_compiler(DEFAULT_DB_ALIAS).as_sql()

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/db/models/sql/compiler.py" in as_sql
  461.                 where, w_params = self.compile(self.where) if self.where is not None else ("", [])

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/db/models/sql/compiler.py" in compile
  393.             sql, params = node.as_sql(self, self.connection)

File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/db/models/sql/where.py" in as_sql
  98.                     raise EmptyResultSet

Exception Type: EmptyResultSet at /manager/booking/bookings/
Exception Value: 

现在我卡住了，我不知道出了什么问题，也不知道如何进一步调试。

为了测试，我尝试传递以下查询字符串:“?state__in=1&source__in=”。在这种情况下，过滤工作正常，但过滤表单显示字段“source__in”的错误“« » 不是有效值”。

此外，这里是utils/views/common.py中的相关mixin:

class ListFilterMixin:

    filters_class = None
    default_filters = None

    @cached_property
    def filters(self):
        return self.get_filters()

    def get_filters(self):
        if self.filters_class:
            qstring = self.request.GET
            if not qstring and self.default_filters:
                qstring = QueryDict(self.default_filters)
            return self.filters_class(
                qstring, self.get_unfiltered_queryset(), request=self.request)
        else:
            return None

    def get_queryset(self):
        print(self.filters.qs.query)  # <--- Line 118
        # ...

    def get_unfiltered_queryset(self):
        return super().get_queryset()

以及booking/views/manager.py中的 View 类:

class BookingListView(ListView):
    """List of all bookings."""

    model = Booking
    default_filters = 'state__in=1'
    filters_class = BookingManagerFilter
    paginate_by = 30
    ordering = '-pk'

    def get_queryset(self):
        queryset = super().get_queryset()  # <--- Line 73
        # ...

此外，您拥有完整的继承树，请注意上面使用的 ListView 是 utils.views.manager.ListView:

class ListView(BulkActionsMixin, ManagerMixin, BaseListView):
    pass

而BaseListView是utils.views.common.ListView:

class ListView(ListFilterMixin, AgencyMixin, ContextMixin, BaseListView):
    pass

最后一个BaseListView是django.views.generic.list.ListView。

---

按照 Kamil 的建议使用 ipdb 进行调试，我注意到一件奇怪的事情可能是导致此行为的原因:

ipdb> next
> /home.tony/.venvs/cocoonr/lib/python3.6/site-packages/django_filters/filters.py(167)filter()
    166     def filter(self, qs, value):
--> 167         if value != self.null_value:
    168             return super().filter(qs, value)

ipdb> self.null_value
'null'
ipdb> value
<QuerySet []>
ipdb> self.field_name
'source'
ipdb> self.lookup_expr
'in'
ipdb> 

所以后续代码，认为source__in不为空，将source__in=empty_queryset添加到过滤器中。我猜 django 然后猜测结果不能评估为非空查询集并保存无用的查询。

是 django-filters 的错误还是我做错了什么？

Answer 1

我认为文档可以回答您的问题:

Filtering by an empty string

It’s not currently possible to filter by an empty string, since empty values are interpreted as a skipped filter.

GET http://localhost/api/my-model?myfield=

进一步在文档中，您有可能的解决方案示例。我把其中一个放在这里

Solution 1: Magic values

You can override the filter() method of a filter class to specifically check for magic values. This is similar to the ChoiceFilter’s null value handling.

GET http://localhost/api/my-model?myfield=EMPTY

class MyCharFilter(filters.CharFilter):
    empty_value = 'EMPTY'

    def filter(self, qs, value):
        if value != self.empty_value:
            return super(MyCharFilter, self).filter(qs, value)

        qs = self.get_method(qs)(**{'%s__%s' % (self.name, self.lookup_expr): ""})
        return qs.distinct() if self.distinct else qs

---

现在我觉得没有足够的信息来解决你的问题。我在你的问题下发表了评论。如果您可以提供额外的信息，将极大地帮助理解正在发生的事情。

这里有一些可以帮助您跟踪此错误的提示:

• 安装 ipdb .它将帮助您逐步执行代码并检查每个变量。

• 在行前放置断点import ipdb;ipdb.set_trace()

  File "/home/tony/.venvs/cocoonr/lib/python3.6/site-packages/django/views/generic/list.py" in get
    142.         self.object_list = self.get_queryset()
  

我怀疑你应该在 https://github.com/carltongibson/django-filter/blob/82a47fb7bbddedf179f110723003f3b28682d7fe/django_filters/filterset.py#L215 中找到罪魁祸首

你可以这样做

class BookingManagerFilter(filters.FilterSet):
    # your previous code here

    def filter_queryset(self, queryset):
        import ipdb;ipdb.set_trace()
        return super(BookingManagerFilter, self)filter_queryset(queryset):

然后运行您的端点，ipdb 将停止该应用程序，您将能够进入代码并检查它。