Django queryset来匹配所有相关对象 [英] Django queryset to match all related objects

问题描述

假设我有一个从椰子到燕子的外国人（即，燕子已经携带了许多椰子，但每只椰子只有一只燕子）。现在我们来说一个从husk_segment到Coconut的ForeignKey。

现在，我有一个husk_segments的列表，我想知道所有这些都被抓住了通过一个特定的燕子。

我可以使用swallow.objects.filter（coconututs_carried__husk_sements__in = husk_segment_list）来显示这个燕子已经在列表中至少抓住了一个外壳段。现在，我怎么能表明燕子所携带的每个外壳都在这个列表中？

解决方案

我可以使用swallow.objects.filter（coconututs_carried__husk_sements__in =
husk_segment_list）来显示这个燕子已经在列表中至少抓住了一个
的外壳段。

<没有，这是错误的，这给你一个从 列表。

如果我明白了，我们正在谈论检查特定的燕子。

所以，从你的描述我猜您的模型看起来像这样：

 类Swallow（models.Model）：
 name = models.CharField（max_length = 100）
 
 
 class Coconut（models.Model）：
 swallow = models.ForeignKey（Swallow，related_name ='coconututs_carried'）
 
 
 
 class HuskSegment（models.M odel）：
 coconut = models.ForeignKey（Coconut，related_name ='husk_segments'）
  

如果您已经拥有了外壳段列表，则需要重新检查燕子片段，因此您无需在查询中解决它。获取燕子的细分，并检查它是否是您的外壳细分列表的超集。

所以我们有：

  #husk_segment_list = [< object：HuskSegment>，< object：HuskSegment>< object：HuskSegment> ...] 
 husk_segments_set = set（（husk.pk for husk in husk_segment_list））
 
 whitey = Swallow.object.get（name ='Neochelidon tibialis'）
 wh_segments_set = set（（value [0] for HuskSegment.objects.filter （coconut__in = whitey.coconuts_carried.all（））。values_list（'id'）））
 
 whitey_has_carried_all = wh_segments_set.issuperset（husk_segments_set）
  

Let's say I have a ForeignKey from Coconut to Swallow (ie, a swallow has carried many coconuts, but each coconut has been carried by only one swallow). Now let's say that I have a ForeignKey from husk_segment to Coconut.

Now, I have a list of husk_segments and I want to find out if ALL of these have been carried gripped by a particular swallow.

I can have swallow.objects.filter(coconuts_carried__husk_sements__in = husk_segment_list) to show that this swallow has gripped at least one husk segment in the list. Now, how can I show that every husk segment that the swallow has ever carried are in this list?

解决方案

I can have swallow.objects.filter(coconuts_carried__husk_sements__in = husk_segment_list) to show that this swallow has gripped at least one husk segment in the list.

No, this is wrong, this gives you a list of swallows which have carried at least one husk segment from *husk_segment_list*.

If I've understood right, we are talking about checking for a specific swallow.

So, from your description I guess your models look something like this:

class Swallow(models.Model):
    name = models.CharField(max_length=100)


class Coconut(models.Model):
    swallow = models.ForeignKey(Swallow, related_name='coconuts_carried')



class HuskSegment(models.Model):
    coconut = models.ForeignKey(Coconut, related_name='husk_segments')

If you already have the husk segment list you need to check againts the swallows segments, there's no reason you need to resolve it in a query. Get the swallows' segments and check if it's a superset of your husk segment list.

So we have:

#husk_segment_list = [<object: HuskSegment>, <object: HuskSegment>, <object: HuskSegment>...]
husk_segments_set = set((husk.pk for husk in husk_segment_list))

whitey = Swallow.object.get(name='Neochelidon tibialis')
wh_segments_set = set((value[0] for value in HuskSegment.objects.filter(coconut__in=whitey.coconuts_carried.all()).values_list('id')))

whitey_has_carried_all = wh_segments_set.issuperset(husk_segments_set)

这篇关于Django queryset来匹配所有相关对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！