模特:
class ListContext(models.Model):
content = models.CharField(max_length=200, blank=True)
我使用south来管理架构迁移。
现在我将之前的模型更改为此模型:
from django.contrib.contenttypes.models import ContentType
class ListContext(models.Model):
content = models.ForeignKey(ContentType, blank=True, null=True)
迁移:
$ python manage.py schemamigration --auto page
~ Changed field content on page.ListContext
+ Added index for ['content'] on page.ListContext
Created 0010_auto__chg_field_listcontext_content.py. You can now apply this migration with: ./manage.py migrate page
在此之前一切都很好:
$ python manage.py migrate page
Running migrations for page:
- Migrating forwards to 0010_auto__chg_field_listcontext_content.
> page:0010_auto__chg_field_listcontext_content
FATAL ERROR - The following SQL query failed: ALTER TABLE "page_page_listcontext" ALTER
COLUMN "content_id" TYPE integer, ALTER COLUMN "content_id" DROP NOT NULL, ALTER COLUMN
"content_id" DROP DEFAULT;
The error was: column "content_id" cannot be cast to type integer
Error in migration: page:0010_auto__chg_field_listcontext_content
我可以猜测在从字符串转换为int期间发生了错误,但是如何避免这种情况并完成迁移呢?
它有什么不同,我不关心保存表中存储的数据。
答案 0 :(得分:4)
如果您手动编辑前进功能:
重命名列:
db.rename_column('sometable', 'content', 'content_old')
然后添加你的专栏:
db.add_column('sometable', 'content', self.gf('django.db.models.fields.IntegerField')(default=0))
然后执行查询,通过查找id来更新新字段。
db.execute("""
UPDATE sometable SET content =
(SELECT FKTable.id FROM FKTable
WHERE (FKTable.content = sometable.content_old AND
sometable.content_old != '')
OR (FKTable.content = 'none' AND sometable.content_old = '')) --Maybe cut the OR out
""")
然后,您必须做一些花哨的事情才能使向后工作正常。