Django 多表继承的南方迁移

我有两个以前从models.Model继承的模型，现在我对它们进行了重构，以从相同的基础模型继承。Django正在为此使用多表继承，我正在尝试为此生成一个模式和数据迁移。数据库中存在需要迁移的现有数据

我知道Django创建了一个OneToOneField，但我不明白它是如何影响数据库中的现有项的

继承前 继承后 迁移 这基本上就是我运行时生成的迁移：

/manage.py模式迁移应用程序--自动

生成的文件：

class Migration(SchemaMigration):
    def forwards(self, orm):
        db.create_table('app_published', (
            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
            ('published_on', self.gf('django.db.models.fields.DateTimeField')()),
        ))
        db.send_create_signal('app', ['Published'])

        db.delete_column('app_blogpost', 'published_on')
        db.delete_column('app_blogpost', 'id')
        db.add_column('app_blogpost', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], unique=True, primary_key=True), keep_default=False)

        db.delete_column('app_audiofile', 'published_on')
        db.delete_column('app_audiofile', 'id')
        db.add_column('app_audiofile', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], unique=True, primary_key=True), keep_default=False)

当我尝试运行它时，它会引发IntegrityError：

column "published_ptr_id" contains null values

---

您需要将其分为三个迁移：

Schemamigration创建app_published表，并添加两个新的published_ptr列。用

null=True

而不是

primary\u key=True

添加这些新列：

db.create_table('app_published', (
    ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
    ('published_on', self.gf('django.db.models.fields.DateTimeField')()),
))
db.add_column('app_blogpost', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=True), keep_default=False)
db.add_column('app_audiofile', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=True), keep_default=False)

数据迁移以迭代现有的音频文件和博客文章。守则基本上是：

for blogpost in orm.BlogPost.objects.all():
    published = orm.Published.objects.create(published_on=blogpost.published_on)
    blogpost.published_ptr = published
    blogpost.save()

for audiofile in orm.AudioFile.objects.all():
    published = orm.Published.objects.create(published_on=audiofile.published_on)
    audiofile.published_ptr = published
    audiofile.save()

Schemamigration从旧模型中删除（现在未使用的）id和列上已发布的\u。此外，在旧型号上，将已发布的\u ptr从

null=True

更改为

primary\u key=True

db.delete_column('app_blogpost', 'published_on')
db.delete_column('app_blogpost', 'id')
db.delete_column('app_audiofile', 'published_on')
db.delete_column('app_audiofile', 'id')

db.alter_column('app_blogpost', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=False))
db.alter_column('app_audiofile', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=False))

db.create_index('app_blogpost', ['published_ptr'], unique=True)
db.create_index('app_audiofile', ['published_ptr'], unique=True)
db.create_primary_key('app_blogpost', ['published_ptr'])
db.create_primary_key('app_audiofile', ['published_ptr'])

for blogpost in orm.BlogPost.objects.all():
    published = orm.Published.objects.create(published_on=blogpost.published_on)
    blogpost.published_ptr = published
    blogpost.save()

for audiofile in orm.AudioFile.objects.all():
    published = orm.Published.objects.create(published_on=audiofile.published_on)
    audiofile.published_ptr = published
    audiofile.save()

db.delete_column('app_blogpost', 'published_on')
db.delete_column('app_blogpost', 'id')
db.delete_column('app_audiofile', 'published_on')
db.delete_column('app_audiofile', 'id')

db.alter_column('app_blogpost', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=False))
db.alter_column('app_audiofile', 'published_ptr', self.gf('django.db.models.fields.related.OneToOneField')(default=None, to=orm['app.Published'], null=False))

db.create_index('app_blogpost', ['published_ptr'], unique=True)
db.create_index('app_audiofile', ['published_ptr'], unique=True)
db.create_primary_key('app_blogpost', ['published_ptr'])
db.create_primary_key('app_audiofile', ['published_ptr'])