使用South重构具有继承性的Django模型

我确实尝试遍历了T Stone概述的解决方案，尽管我认为这是一个了不起的入门，并解释了应该如何做，但我遇到了一些问题。

我认为大多数情况下，你不再需要为父类创建表条目，即你不需要

new_movie.videofile_ptr = orm['media.VideoFile'].objects.create()

不再。Django现在会自动为你执行此操作（如果你有非null字段，则以上内容对我不起作用，并给我一个数据库错误）。

我认为这可能是由于django和south的变化所致，这是一个适用于Django 1.2.3和south 0.7.1的ubuntu 10.10的版本。这些模型有些不同，但是你将获得要点：

初始设置
post1 / models.py：

class Author(models.Model):    first = models.CharField(max_length=30)    last = models.CharField(max_length=30)class Tag(models.Model):    name = models.CharField(max_length=30, primary_key=True)class Post(models.Model):    created_on = models.DateTimeField()    author = models.ForeignKey(Author)    tags = models.ManyToManyField(Tag)    title = models.CharField(max_length=128, blank=True)    content = models.TextField(blank=True)

post2 / models.py：

class Author(models.Model):    first = models.CharField(max_length=30)    middle = models.CharField(max_length=30)    last = models.CharField(max_length=30)class Tag(models.Model):    name = models.CharField(max_length=30)class Category(models.Model):    name = models.CharField(max_length=30)class Post(models.Model):    created_on = models.DateTimeField()    author = models.ForeignKey(Author)    tags = models.ManyToManyField(Tag)    title = models.CharField(max_length=128, blank=True)    content = models.TextField(blank=True)    extra_content = models.TextField(blank=True)    category = models.ForeignKey(Category)

显然有很多重叠之处，因此我想将通用性分解为通用的后期模型，而只保留其他模型类中的差异。

新设置：

genpost / models.py：

class Author(models.Model):    first = models.CharField(max_length=30)    middle = models.CharField(max_length=30, blank=True)    last = models.CharField(max_length=30)class Tag(models.Model):    name = models.CharField(max_length=30, primary_key=True)class Post(models.Model):    created_on = models.DateTimeField()    author = models.ForeignKey(Author)    tags = models.ManyToManyField(Tag)    title = models.CharField(max_length=128, blank=True)    content = models.TextField(blank=True)

post1 / models.py：

import genpost.models as gpclass SimplePost(gp.Post):    class meta:        proxy = Truepost2 / models.py：import genpost.models as gpclass Category(models.Model):    name = models.CharField(max_length=30)class ExtPost(gp.Post):    extra_content = models.TextField(blank=True)    category = models.ForeignKey(Category)

如果你想继续前进，首先需要将这些模型推向南方：

$./manage.py schemamigration post1 --initial$./manage.py schemamigration post2 --initial$./manage.py migrate

迁移数据
怎么做呢？首先编写新的应用程序genpost，然后向南进行初始迁移：

$./manage.py schemamigration genpost --initial

（我$用来表示shell提示符，所以请不要键入。）

接下来，分别在post1 / models.py和post2 / models.py中创建新类SimplePost和ExtPost（请不要删除其余的类）。然后也为这两个创建schemamigrations：

$./manage.py schemamigration post1 --auto$./manage.py schemamigration post2 --auto

现在我们可以应用所有这些迁移：

$./manage.py migrate

让我们开始讨论，将数据从post1和post2迁移到genpost：

$./manage.py datamigration genpost post1_and_post2_to_genpost --freeze post1 --freeze post2

然后编辑genpost / migrations / 0002_post1_and_post2_to_genpost.py：

class Migration(DataMigration):    def forwards(self, orm):        #         # Migrate common data into the new genpost models        #        for auth1 in orm['post1.author'].objects.all(): new_auth = orm.Author() new_auth.first = auth1.first new_auth.last = auth1.last new_auth.save()        for auth2 in orm['post2.author'].objects.all(): new_auth = orm.Author() new_auth.first = auth2.first new_auth.middle = auth2.middle new_auth.last = auth2.last new_auth.save()        for tag in orm['post1.tag'].objects.all(): new_tag = orm.Tag() new_tag.name = tag.name new_tag.save()        for tag in orm['post2.tag'].objects.all(): new_tag = orm.Tag() new_tag.name = tag.name new_tag.save()        for post1 in orm['post1.post'].objects.all(): new_genpost = orm.Post() # Content new_genpost.created_on = post1.created_on new_genpost.title = post1.title new_genpost.content = post1.content # Foreign keys new_genpost.author = orm['genpost.author'].objects.filter(         first=post1.author.first,last=post1.author.last)[0] new_genpost.save() # Needed for M2M updates for tag in post1.tags.all():     new_genpost.tags.add(  orm['genpost.tag'].objects.get(name=tag.name)) new_genpost.save() post1.delete()        for post2 in orm['post2.post'].objects.all(): new_extpost = p2.ExtPost()  new_extpost.created_on = post2.created_on new_extpost.title = post2.title new_extpost.content = post2.content # Foreign keys new_extpost.author_id = orm['genpost.author'].objects.filter(         first=post2.author.first,         middle=post2.author.middle,         last=post2.author.last)[0].id new_extpost.extra_content = post2.extra_content new_extpost.category_id = post2.category_id # M2M fields new_extpost.save() for tag in post2.tags.all():     new_extpost.tags.add(tag.name) # name is primary key new_extpost.save() post2.delete()        # Get rid of author and tags in post1 and post2        orm['post1.author'].objects.all().delete()        orm['post1.tag'].objects.all().delete()        orm['post2.author'].objects.all().delete()        orm['post2.tag'].objects.all().delete()    def backwards(self, orm):        raise RuntimeError("No backwards.")

现在应用这些迁移：

$./manage.py migrate

接下来，你可以从post1 / models.py和post2 / models.py中删除现在多余的部分，然后创建schemamigrations以将表更新为新状态：

$./manage.py schemamigration post1 --auto$./manage.py schemamigration post2 --auto$./manage.py migrate

就是这样！希望所有这些都能奏效，并且你已经重构了模型。