django-mptt引发django.db.utils.IntegrityError:列"lft"中的空值.违反非空约束 [英] django-mptt raises django.db.utils.IntegrityError: null value in column "lft" violates not-null constraint
问题描述
条件:Django == 1.8.7иdjango-mptt == 0.8.0.
Conditions: Django==1.8.7 и django-mptt==0.8.0.
有一个模型:
class Tree(mptt_models.MPTTModel):
name = models.CharField(max_length=120, unique=True)
slug = models.SlugField(max_length=256, unique=True)
parent = mptt_models.TreeForeignKey('self', null=True, blank=True,
related_name='children', db_index=True)
class MPTTMeta:
order_insertion_by = ['name']
我可以用管理界面填充它并显示在网站页面上.
I can fill it with admin interface and show on a site pages.
我可以用django shell填充它:
I can fill it with django shell:
Python 2.7.3 (default, Jun 22 2015, 19:43:34)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from src.catalog.models import Tree
>>> Tree.objects.create(name='1', slug='2')
<Tree: 1>
>>> Tree.objects.all()
[<Tree: 1>]
我编写了一个迁移,该迁移使用旧模型中的信息填充了Tree模型:
I have wrote a migration that fills the Tree model using information from legacy models:
def propagate_tree(app_registry, schema_editor):
Category = app_registry.get_model('catalog', 'Category')
Tree = app_registry.get_model('catalog', 'Tree')
for category in Category.objects.all():
parent = Tree.objects.create(name=category.title, slug=category.slug)
for group in category.group_set.all():
Tree.objects.create(parent=parent, name=group.title, slug=group.slug)
我遇到以下错误:
django.db.utils.IntegrityError: null value in column "lft" violates not-null constraint
在执行该行时:
parent = Tree.objects.create(name=category.title, slug=category.slug)
仍然无法理解此错误的原因:(
Still can not understand the reason of this error :(
推荐答案
我遇到了同样的问题,原因是使用app_registry导入模型. 在迁移中将其替换:
I've just come across the same issue, and the reason is the Model import using the app_registry. Replace this in the migration:
Tree = app_registry.get_model('catalog', 'Tree')
具有常规导入功能,就像在shell中一样.
with the normal import, as you are doing in the shell.
from src.catalog.models import Tree
它应该像魅力一样工作.
And it should work like charm.
但是,我不知道为什么第一个不起作用,因为就我而言,这是在迁移文件中导入模型的首选方式.
However, I don't know why the first one doesn't work, because, as far as I'm concerned, it's the preferred way of importing Models in migration files.
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