南移多表继承 [英] South migration for multi-table inheritance
问题描述
我知道Django创建了一个OneToOneField,但是我不明白如何在数据库中存在需要迁移的现有数据它影响数据库中的现有项目。
继承之前
BlogPost(models.Model):
name = models.CharField()
published_on = models.DateTimeField()
class AudioFile(models.Model):
file = models.FileField()
published_on = models.DateTimeField()
继承后< h2>
类已发布(models.Model):
published_on = models.DateTimeField()
class BlogPost(发布):
name = models.CharField()
class AudioFile(发布):
file = models.FileField()
类已发布(models.Model):
published_on = models.DateTimeField()
class BlogPost(发布):
name = models.CharField()
class AudioFile(发布):
file = models.FileField()
迁移
这基本上是我运行时生成的迁移: p>
./ manage.py schemamigration ap p -auto
。
生成的文件:
class Migration(SchemaMigration):
def forward(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',['发布'])
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('a pp_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,它会引发一个IntegrityError:
列published_ptr_id包含空值
您将需要将其分为三个迁移:
-
Schemamigration以创建app_published表,并添加两个新的published_ptr列。使用
null = True
添加这些新列,而不是使用primary_key = True
:db.create_table('app_published',(
('id',self.gf('django.db.models.fields.AutoField') ($)
('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)
-
数据迁移以遍历现有的音频文件和博客。代码基本上是:
for orm.BlogPost.objects.all():
published = orm。发布的.objects.create(published_on = blogpost.published_on)
blogpost.published_ptr =已发布
blogpost.save()
在orm.AudioFile.objects.all()中的audiofile :
published = orm.Published.objects.create(published_on = audiofile.published_on)
audiofile.published_ptr = published
audiofile.save()
-
模式迁移以从旧模型中删除(现在未使用)的id和published_on列。另外,在旧模型上,将published_ptr从
null = True
更改为primary_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')(默认=无,为= ORM [ 'app.Published'],NULL = FALSE))
db.alter_column( 'app_audiofile',published_ptr ,self.gf( 'django.db.models.fields.related.OneToOneField')(默认=无,为= ORM [ 'app.Published'],NULL = FALSE))
分贝.create_index( 'app_blogpost',[ 'published_ptr'],独特=真)
db.create_index( 'app_audiofile',[ 'published_ptr'],独特=真)
db.create_primary_key( 'app_blogpost' ,[ 'published_ptr'])
db.create_primary_key('app_audiofile ,[ published_ptr])
Schemamigration to create the app_published table, and add your two new published_ptr columns. Add these new columns with
null=True
instead of withprimary_key=True
: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)
Datamigration to iterate over your existing audiofiles and blogposts. The code is basically:
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 to remove the (now unused) id and published_on columns from your old models. Also, change published_ptr from
null=True
toprimary_key=True
on the old models.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'])
醇>
I have a two models that previously inherited from models.Model and now I've refactored them to inherit from the same base model. Django is using multi-table inheritance for this and I'm trying to generate a schema and data migration for this. There is existing data in the database which needs to be migrated.
I know that Django creates a OneToOneField, but I don't understand how it affects existing items in the database.
Before Inheritance
class BlogPost(models.Model):
name = models.CharField()
published_on = models.DateTimeField()
class AudioFile(models.Model):
file = models.FileField()
published_on = models.DateTimeField()
After inheritance
class Published(models.Model):
published_on = models.DateTimeField()
class BlogPost(Published):
name = models.CharField()
class AudioFile(Published):
file = models.FileField()
Migration
This was basically the migration that was generated when I ran:
./manage.py schemamigration app --auto
.
Generated file:
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)
When I try to run it, it raises an IntegrityError:
column "published_ptr_id" contains null values
You're going to need to break that into three migrations:
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