南迁和多对多地区的变化 [英] South migrations and changes to many-to-may fields

问题描述

我正在开发一个应用程序，用于向客户发送通讯。我有一个模型定义如下

  from django.auth.models import User 
 
 class Newsletter 
 owner = models.ForeignKey（User，related_name ='+'，blank = False）
 sent = models.BooleanField（default = False）
 date_created = models.DateTimeField （auto_now_add = True）
 date_sent = models.DateTimeField（null = True） 
 subject = models.CharField（max_length = 255）
 content = HTMLField（）
 recipient = models.ManyToManyField（User，related_name ='+'）
  

稍后，我发现我可能需要将这些发送给没有用户帐户的人，所以我定义了一个电子邮件模型

  class Email（models.Model）： 
 email = models.CharField（max_length = 255）
  

并将收件人字段更改为

  recipients = models.ManyToManyField（Email，related_name ='+'）
  / pre> 
 
 
之后，我运行了schemamigration命令，但South声称没有更改。我已经做了几次手动操作表和索引的尝试，但在某种程度上，由于它是一个新的应用程序，我可以删除所有现有的表，删除所有的数据并从头重新创建初始迁移。这是一个问题，如果我真的需要保留数据，我该怎么做这样的迁移。
解决方案
如果你需要保存数据，您将需要将其拆分为3个迁移（模式，数据，模式），如下所示：
  class Migration模式迁移）
 
 def转发（self，orm）：
 db.add_column（
 u'yourapp_newsletter_recipients'，
'email_id'，
 self。 gf（
'django.db.models.fields.related.ForeignKey'
）（to = orm.Email）
）
  
请注意，您应该在迁移模型属性中使用旧模式。
 
 
 
然后，您的数据迁移将填充电子邮件字段。然后再架构迁移：
  class Migration（SchemaMigration）：
 
 def forward（self，orm） ：
 db.delete_column（u'yourapp_newsletter_recipients'，'user_id'）
  
在这一个您应该已经在迁移模型中的收件人字段中具有正确的m2m字段['newslatter'] 
 
I was working on an app that is supposed to send newsletters to customers. I had a model defined like this
from django.auth.models import User

class Newsletter(models.Model):                                                                  
    owner = models.ForeignKey(User, related_name='+', blank=False)                                                                                                                                                  
    sent = models.BooleanField(default=False)                                                                                                                                                                       
    date_created = models.DateTimeField(auto_now_add=True)                                                                                                                                                          
    date_sent = models.DateTimeField(null=True)                                                                                                                                                                     
    subject = models.CharField(max_length=255)                                                                                                                                                                      
    content = HTMLField()                                                                                                                                                                                           
    recipients = models.ManyToManyField(User, related_name='+')                                                                                                                                                    
Later on, I found out that I might need to send these to people who do not have user accounts, so I defined an email model
class Email(models.Model):                                                                                                                                                                                          
    email = models.CharField(max_length=255)                                                          
and changed the recipients field to read 
recipients = models.ManyToManyField(Email, related_name='+')
After this, I ran schemamigration command, but South claimed that there are no changes. I have made several attempts to manually manipulate tables and indexes, but at some point figured that since it is a new app, I can just drop all the existing tables, remove all igrations and recreate initial migration from scratch. This poses a question though, how do I do a migration like this if I really need to preserve the data.
解决方案
If you need to preserve data you will need to split it into 3 migrations (schema, data, schema) like this:
class Migration(SchemaMigration):

    def forwards(self, orm):
        db.add_column(
            u'yourapp_newsletter_recipients',
            'email_id',
            self.gf(
                'django.db.models.fields.related.ForeignKey'
            )(to=orm.Email)
        )
Notice that you should have your old schema in the migration's models property.

Then your data migration that fills the email field. Then schema migration again:
class Migration(SchemaMigration):

    def forwards(self, orm):
        db.delete_column(u'yourapp_newsletter_recipients', 'user_id')
In this one you should already have correct m2m field for recipients field in the migration's models['newslatter']

                        
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