Django：存储分层数据

发布于 2024-09-12 03:53:22 字数 693 浏览 9 评论 0原文

我正在尝试将文档的各个部分存储在 Django 应用程序中。该模型如下所示：

class Section(models.Model):
  project = models.ForeignKey(Project)
  parent_section = models.ForeignKey('Section', blank=True, null=True, related_name='child_set')
  predecessor_section = models.ForeignKey('Section', blank=True, null=True, related_name='predecessor_set')
  name = models.CharField(max_length=100)
  text = models.TextField(blank=True, null=True)

我创建了很多部分，链接它们（parent_section、predecessor_section）并通过调用它们的每个保存方法来存储它们。但是，当我保存后查看表时，parent_section_id 和predecessor_section_id 未设置，即使我在保存之前附加了对象。

我认为这与以下事实有关：某些parent_section实例没有分配id，因为它们的实例尚未存储，但使用手动事务无法解决问题。

对此有什么想法吗？

干杯，最大限度

原文

I'm trying to store sections of a document in a Django app. The model looks like:

class Section(models.Model):
  project = models.ForeignKey(Project)
  parent_section = models.ForeignKey('Section', blank=True, null=True, related_name='child_set')
  predecessor_section = models.ForeignKey('Section', blank=True, null=True, related_name='predecessor_set')
  name = models.CharField(max_length=100)
  text = models.TextField(blank=True, null=True)

I create a whole lot of sections, link them (parent_section, predecessor_section) and store them by calling each of their save methods. However, when I look into the table after saving it, the parent_section_id and the predecessor_section_id are not set, even though I had objects attached to them before saving.

I assume it has to do with the fact that some parent_section instances don't have an id assigned as their instance hasn't been stored yet, but using manual transactions couldn't solve the problem.

Any thoughts on that?

Cheers,
Max

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飘逸的'云 2024-09-19 03:53:22

在将对象保存到 Django ORM 中之前，它们没有 id。

所以我想说你需要 save() 对象，然后在父/子部分中引用它（并重新保存这些部分）。

然而，将 prec 和 next 作为指针存储的另一种选择是存储 sequence_index （间隔 10 以允许进一步插入而无需重新排序）并按此索引排序。

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擦肩而过的背影 2024-09-19 03:53:22

尝试对所有对象执行 save() 操作，然后更新它们的关系，然后再次 save() 所有对象。

当您分配外键时，相关（目标）对象的 ID 会被复制。因为在分配关系（parent_section、predecessor_section）时，相关对象还没有 id，所以你会得到一个奇怪的结果：

A = Section(name='A')
B = Section(name='B')
B.parent_section = A
A.save() 
B.save()
B.parent_section # this will say A
B.parent_section_id # this will say **None**

但这应该有效：

A = Section(name='A')
B = Section(name='B')
A.save() 
B.save()
B.parent_section = A
B.parent_section # this will say A
B.parent_section_id # this will say A.id
B.save() # don't forget this one :)

Try doing a save() on all the objects, then update their relations, and then save() all of them again.

When you assign a foreignkey, the related (target) object's id is copied. since at the moment of assigning the relations (parent_section, predecessor_section) the related objects don't have an id yet, you get a funky result:

A = Section(name='A')
B = Section(name='B')
B.parent_section = A
A.save() 
B.save()
B.parent_section # this will say A
B.parent_section_id # this will say **None**

But this should work:

A = Section(name='A')
B = Section(name='B')
A.save() 
B.save()
B.parent_section = A
B.parent_section # this will say A
B.parent_section_id # this will say A.id
B.save() # don't forget this one :)

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