规范答案
出现问题的原因是即使 Django 看到模型被重命名并且子类需要指针更新，但它不能正确地执行这些更新。在撰写本文时，有一个 PR 可以将其添加到 Django（https://github.com/django/django/pull/13021，最初是 11222），但在此之前，解决方案是暂时“欺骗”Django 认为子类实际上是没有任何继承，并通过执行以下步骤手动影响更改：
- 手动将自动生成的继承指针从
superclass_ptr 重命名为 newsuperclass_ptr（在这种情况下，baseproduct_ptr 变为 product_prt），然后
- 通过为子类重写
.bases 属性并告诉 Django 重新加载它们，让 Django 认为子类只是通用模型实现，然后
- 将超类重命名为新名称（在这种情况下，
BaseProduct 变为 Product），然后最后
- 更新
newsuperclass_ptr 字段，使其指向新的超类名称，确保指定auto_created=True 和parent_link=True。
在最后一步中，第一个属性应该在那里，主要是因为 Django 自动生成指针，我们不希望 Django 能够告诉我们曾经欺骗过它并做了我们自己的事情，而第二个属性在那里因为parent_link 是 Django 在运行时正确连接模型继承所依赖的字段。
因此，比 manage makemigrations 多几个步骤，但每个步骤都很简单，我们可以通过编写一个自定义迁移文件来完成所有这些。
使用问题帖子中的名称：
# Custom Django 2.2.12 migration for handling superclass model renaming.
from django.db import migrations, models
import django.db.models.deletion
# with a file called custom_operations.py in our migrations dir:
from .custom_operations import AlterModelBases
class Migration(migrations.Migration):
dependencies = [
('yourapp', '0001_initial'),
# Note that if the last real migration starts with 0001,
# this migration file has to start with 0002, etc.
#
# Django simply looks at the initial sequence number in
# order to build its migration tree, so as long as we
# name the file correctly, things just work.
]
operations = [
# Step 1: First, we rename the parent links in our
# subclasses to match their future name:
migrations.RenameField(
model_name='generalproduct',
old_name='baseproduct_ptr',
new_name='product_ptr',
),
migrations.RenameField(
model_name='softwareproduct',
old_name='baseproduct_ptr',
new_name='product_ptr',
),
# Step 2: then, temporarily set the base model for
# our subclassses to just `Model`, which makes
# Django think there are no parent links, which
# means it won't try to apply crashing logic in step 3.
AlterModelBases("GeneralProduct", (models.Model,)),
AlterModelBases("SoftwareProduct", (models.Model,)),
# Step 3: Now we can safely rename the superclass without
# Django trying to fix subclass pointers:
migrations.RenameModel(
old_name="BaseProduct",
new_name="Product"
),
# Step 4: Which means we can now update the `parent_link`
# fields for the subclasses: even though we altered
# the model bases earlier, this step will restore
# the class hierarchy we actually need:
migrations.AlterField(
model_name='generalproduct',
name='product_ptr',
field=models.OneToOneField(
auto_created=True,
on_delete=django.db.models.deletion.CASCADE,
parent_link=True, primary_key=True,
serialize=False,
to='buyersguide.Product'
),
),
migrations.AlterField(
model_name='softwareproduct',
name='product_ptr',
field=models.OneToOneField(
auto_created=True,
on_delete=django.db.models.deletion.CASCADE,
parent_link=True,
primary_key=True,
serialize=False,
to='buyersguide.Product'
),
),
]
关键步骤是继承“破坏”：我们告诉 Django 子类继承自models.Model，因此重命名超类将使子类完全不受影响（而不是 Django 尝试更新继承指针本身），但我们实际上并没有更改数据库中的任何内容。我们只对当前正在运行的代码进行更改，因此如果我们退出 Django，就好像从未进行过更改一样。
因此，为了实现这一点，我们使用了一个自定义的ModelOperation，它可以在运行时将一个（ny）类的继承更改为一个（ny 集合）不同的超类：
# contents of yourapp/migrations/custom_operations.py
from django.db.migrations.operations.models import ModelOperation
class AlterModelBases(ModelOperation):
reduce_to_sql = False
reversible = True
def __init__(self, name, bases):
self.bases = bases
super().__init__(name)
def state_forwards(self, app_label, state):
"""
Overwrite a models base classes with a custom list of
bases instead, then force Django to reload the model
with this (probably completely) different class hierarchy.
"""
state.models[app_label, self.name_lower].bases = self.bases
state.reload_model(app_label, self.name_lower)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
pass
def database_backwards(self, app_label, schema_editor, from_state, to_state):
pass
def describe(self):
return "Update %s bases to %s" % (self.name, self.bases)
有了这个自定义迁移文件和我们的custom_operations.py，我们需要做的就是更新我们的代码以反映新的命名方案：
class Product(models.Model):
name = models.CharField()
description = models.CharField()
class GeneralProduct(Product):
pass
class SoftwareProduct(Product):
pass
然后应用manage migrate，它将根据需要运行并更新所有内容。
注意：取决于您是否“预先构造”了代码以准备重命名，使用如下方式：
class BaseProduct(models.Model):
name = models.CharField()
description = models.CharField()
# "handy" aliasing so that all code can start using `Product`
# even though we haven't renamed actually renamed this class yet:
Product = BaseProduct
class GeneralProduct(Product):
pass
class SoftwareProduct(Product):
pass
您可能需要在其他类中将 ForeignKey 和 ManyToMany 关系更新为 Product，添加显式添加 models.AlterField 指令以将 BaseProduct 更新为 Product：
...
migrations.AlterField(
model_name='productrating',
name='product',
field=models.ForeignKey(
on_delete=django.db.models.deletion.CASCADE,
to='yourapp.Product'
),
),
...
原答案
哦，是的，这是一个棘手的问题。但是我在我的项目中已经解决了，我就是这样做的。
1) 删除新创建的迁移并回滚您的模型更改
2) 使用 parent_link 选项将隐式父链接字段更改为显式。我们需要这个在后面的步骤中手动将我们的字段重命名为propper name
class BaseProduct(models.Model):
...
class GeneralProduct(BaseProduct):
baseproduct_ptr = models.OneToOneField(BaseProduct, django.db.models.deletion.CASCADE, parent_link=True, primary_key=True)
class SoftwareProduct(BaseProduct):
baseproduct_ptr = models.OneToOneField(BaseProduct, django.db.models.deletion.CASCADE, parent_link=True, primary_key=True)
3) 通过makemigrations 生成迁移并得到类似的东西
...
migrations.AlterField(
model_name='generalproduct',
name='baseproduct_ptr',
field=models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='BaseProduct'),
),
migrations.AlterField(
model_name='softwareproduct',
name='baseproduct_ptr',
field=models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='BaseProduct'),
)
...
4) 现在您有了指向父模型的显式链接，您可以将它们重命名为 product_ptr，这将匹配您想要的链接名称
class GeneralProduct(BaseProduct):
product_ptr = models.OneToOneField(BaseProduct, django.db.models.deletion.CASCADE, parent_link=True, primary_key=True)
class SoftwareProduct(BaseProduct):
product_ptr = models.OneToOneField(BaseProduct, django.db.models.deletion.CASCADE, parent_link=True, primary_key=True)
5) 通过makemigrations 生成迁移并得到类似的东西
...
migrations.RenameField(
model_name='generalproduct',
old_name='baseproduct_ptr',
new_name='product_ptr',
),
migrations.RenameField(
model_name='softwareproduct',
old_name='baseproduct_ptr',
new_name='product_ptr',
),
...
6) 现在最棘手的部分是我们需要添加新的迁移操作（源代码可以在这里找到https://github.com/django/django/pull/11222）并放入我们的代码，我个人在我的项目中有contrib 包，我把所有员工都放在那里像这样
contrib/django/migrations.py中的文件
# https://github.com/django/django/pull/11222/files
# https://code.djangoproject.com/ticket/26488
# https://code.djangoproject.com/ticket/23521
# https://code.djangoproject.com/ticket/26488#comment:18
# https://github.com/django/django/pull/11222#pullrequestreview-233821387
from django.db.migrations.operations.models import ModelOperation
class DisconnectModelBases(ModelOperation):
reduce_to_sql = False
reversible = True
def __init__(self, name, bases):
self.bases = bases
super().__init__(name)
def state_forwards(self, app_label, state):
state.models[app_label, self.name_lower].bases = self.bases
state.reload_model(app_label, self.name_lower)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
pass
def database_backwards(self, app_label, schema_editor, from_state, to_state):
pass
def describe(self):
return "Update %s bases to %s" % (self.name, self.bases)
7) 现在我们准备重命名父模型
class Product(models.Model):
....
class GeneralProduct(Product):
pass
class SoftwareProduct(Product):
pass
8) 通过makemigrations 生成迁移。确保添加DisconnectModelBases 步骤，即使成功生成迁移也不会自动添加。如果这没有帮助，您可以尝试手动创建--empty。
from django.db import migrations, models
import django.db.models.deletion
from contrib.django.migrations import DisconnectModelBases
class Migration(migrations.Migration):
dependencies = [
("contenttypes", "0002_remove_content_type_name"),
("products", "0071_auto_20200122_0614"),
]
operations = [
DisconnectModelBases("GeneralProduct", (models.Model,)),
DisconnectModelBases("SoftwareProduct", (models.Model,)),
migrations.RenameModel(
old_name="BaseProduct", new_name="Product"
),
migrations.AlterField(
model_name='generalproduct',
name='product_ptr',
field=models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='products.Product'),
),
migrations.AlterField(
model_name='softwareproduct',
name='product_ptr',
field=models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='proudcts.Product'),
),
]
注意：毕竟，您不需要明确的parent_link 字段。所以你可以删除它们。我实际上是在第 7 步中完成的。