Django：如果搜索空列表

发布于 2025-02-12 04:04:55 字数 822 浏览 0 评论 0原文

具有此代码序列：

queryset = self.filter(
            brand_id__in=(
                UserObjectPermission.objects.filter(
                    content_type=brand_ctype,
                    user=user,
                ).values_list('object_pk')
            )
        )

如果没有userObjectpermissign对象与过滤器content_type = brand_ctype，user = user =用户匹配，则最终结果将为空QUERYSET，因为Brand_ID __in将在[空QuerySet]中搜索。

但是我需要相反。如果此过滤器没有userObjectPermision对象（content_type = brand_ctype，user = user = user），则返回所有对象，即忽略此过滤器（

brand_id__in=(UserObjectPermission.objects.filter(
                    content_type=brand_ctype,
                    user=user,
                ).values_list('object_pk')
            )

我需要brand_id__in filter才能运行至少只有在QuerySet中的一个对象。

原文

Having this code sequence:

queryset = self.filter(
            brand_id__in=(
                UserObjectPermission.objects.filter(
                    content_type=brand_ctype,
                    user=user,
                ).values_list('object_pk')
            )
        )

If there is no UserObjectPermission object that matches the filter content_type=brand_ctype, user=user then the end result will be empty queryset, because brand_id __in will search in [empty queryset].

But I need the reverse. If there is no UserObjectPermision object for this filter (content_type=brand_ctype, user=user) then return all objects, that is, ignore this filter (

brand_id__in=(UserObjectPermission.objects.filter(
                    content_type=brand_ctype,
                    user=user,
                ).values_list('object_pk')
            )

I need the brand_id__in filter to run only if there is at least one object in the queryset.

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彻夜缠绵 2025-02-19 04:04:55

您可以尝试（|）操作员

from django.db.models import Q, Exists

brands_qs = UserObjectPermission.objects.filter(
    content_type=brand_ctype,
    user=user,
).values_list('object_pk')

queryset = self.filter(
    Q(brand_id__in=brands_qs) | ~Exists(brands_qs)
)

you can try the OR (|) operator

from django.db.models import Q, Exists

brands_qs = UserObjectPermission.objects.filter(
    content_type=brand_ctype,
    user=user,
).values_list('object_pk')

queryset = self.filter(
    Q(brand_id__in=brands_qs) | ~Exists(brands_qs)
)

回复收藏 0 原文

撑一把青伞 2025-02-19 04:04:55

您可以检查QuerySet是否包含任何项目：

brands = UserObjectPermission.objects.filter(
    content_type=brand_ctype,
    user=user,
).values_list('object_pk')

if brands:
    queryset = queryset.filter(brand_id__in=brands)

You can check if the queryset contains any items:

brands = UserObjectPermission.objects.filter(
    content_type=brand_ctype,
    user=user,
).values_list('object_pk')

if brands:
    queryset = queryset.filter(brand_id__in=brands)

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