其他应用程序中的 Django 迁移文件? [英] Django migration file in an other app?

问题描述

让我们想象以下简化的 Django 项目:

Let's imagine a following simplified Django project:

<root>/lib/python2.7/site-packages/externalapp/shop
<root>/myapp

myapp 还通过添加一些字段来扩展 externalapp.shop.models 模型.manage.py makemigrations 确实生成了以下名为 0004_auto_20150410_2001.py 的架构迁移文件:

myapp also extends externalapp.shop.models models by adding a few fields. manage.py makemigrations did generated following schema migration file called 0004_auto_20150410_2001.py:

from __future__ import unicode_literals
from django.db import models, migrations


class Migration(migrations.Migration):

    # __init__ is added by me as an attempt how to tell django's
    # migration loader operations are for the different application
    def __init__(self, name, app_label):
        super(Migration, self).__init__(name, 'shop')

    dependencies = [
        ('myapp', '__first__'),
        ('shop', '0003_auto_20150408_0958'),
    ]

    operations = [
        migrations.AddField(
            model_name='product',
            name='vat',
            field=models.ForeignKey(to='myapp.VAT', null=True),
        ),
    ]

如果上面的迁移schema默认放在/lib/python2.7/site-packages/externalapp/shop/migrations/路径下，manage.py migrate 成功，表字段添加正确.

If the above migration schema is placed in <root>/lib/python2.7/site-packages/externalapp/shop/migrations/ path by default, manage.py migrate succeeds and table fields are correctly added.

但是，如果我确实将上面的迁移文件移动到 myapp/migrations/，下面的 manage.py migrate 会失败并显示

However if I do move the above migration file into myapp/migrations/, following manage.py migrate fails with

django.core.management.base.CommandError:检测到冲突的迁移(0001_initial、0004_auto_20150410_2001 in myapp).要修复它们，请运行python manage.py makemigrations --merge"

我不太明白的错误消息并建议 makemigrations --merge 失败并预期:

error message I can't quite understand and suggested makemigrations --merge fails with expected:

ValueError: 找不到集合的共同祖先([u'0001_initial', u'0004_auto_20150410_2001'])

我试图覆盖 migrations.Migration.__init__ 来改变派生的 app_label 但似乎迁移加载程序忽略了它.

I've tried to override migrations.Migration.__init__ to alter derived app_label but seems migration loader ignores it.

如何调整迁移文件使其可以从其他应用程序工作?原因是在生产中 externalapp 源不能直接接触，是只读的.

How adjust migration file so it can work from other application ? The reason is in production externalapp sources can't be directly touched, are read only.

推荐答案

要在 Django 项目中移动迁移文件，例如注入其他应用程序的模型，您需要在 django.db 中确保.migrations.Migration 后代:

To move a migration file around a Django project, like in case of injecting models of other applications, you need to ensure in your django.db.migrations.Migration descendant:

• 显式设置应用程序名称，因为迁移加载程序由迁移文件所在的应用程序自动派生，否则将尝试在不同模型上执行操作
• 通知迁移记录器它为其他应用程序提供迁移，否则它仍将认为迁移未应用(有关已应用迁移的记录存储在一个表中，当前名为 django_migrations)

我已经解决了迁移初始值设定项中的问题，它可能如下所示:

I've solved the issue in migration initializer which may look like:

from django.db import migrations

TARGET_APP = 'shop'    # application label migration is for

class Migration(migrations.Migration):

    def __init__(self, name, app_label):
        # overriding application operated upon
        super(Migration, self).__init__(name, TARGET_APP)

    # specify what original migration file it replaces
    # or leave migration loader confused about unapplied migration
    replaces = ((TARGET_APP, __module__.rsplit('.', 1)[-1]),)

它确实对我有用，并且找到了足够通用的方式.

It does work for me and find it enough generic way.

如果可能，渴望听到更好/更简单的解决方案.

Eager to hear about a better/simpler solution if possible.

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