为什么南迁失败了？

Question

我有一个刚刚创建的空白MySQL数据库。south在我的INSTALLED_APPS中。

我运行：

$ ./manage.py syncdb
...
Creating table some_app_table

You just installed Django's auth system, which means you don't have any superusers defined.
...
Superuser created successfully.
Installing custom SQL ...
Installing indexes ...
Installed 0 object(s) from 0 fixture(s)

Synced:
 > django.contrib.auth
 > django.contrib.contenttypes
...

Not synced (use migrations):
 - myapp
...

$ ./manage.py schemamigration myapp --initial
 + Added model myapp.Model
...
Created 0003_initial.py. You can now apply this migration with: ./manage.py migrate myapp

$ ./manage.py migrate myapp
Running migrations for myapp:
 - Migrating forwards to 0003_initial.
 > skan:0001_initial
 > skan:0002_initial
FATAL ERROR - The following SQL query failed: CREATE TABLE `myapp_model` (`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `user_id` integer NULL, `name` varchar(200) NOT NULL);
The error was: (1050, "Table 'myapp_model' already exists")

到底怎么回事？为什么South不能正确初始化？

Answer 1

您已经定义了一些迁移：initial (正如预期的那样)仅用于初始迁移。

您的syncdb输出显示：

Not synced (use migrations):
 - myapp

这表明南方正在像预期的那样工作。但是，然后你会这样做：

$ ./manage.py schemamigration myapp --initial
+ Added model myapp.Model
...
Created 0003_initial.py. You can now apply this migration with: ./manage.py migrate myapp

请注意0003-prefix:这(很可能)表示已经定义了迁移。下一条命令的输出确认了这一点：

$ ./manage.py migrate myapp
Running migrations for myapp:
 - Migrating forwards to 0003_initial.
 > skan:0001_initial
 > skan:0002_initial
 <snip>

换句话说，您已经有两个initial迁移，其中至少有一个将创建该表。您的#3迁移再次尝试这样做，但失败了，因为表当然已经存在了。

您需要做的是只在创建Django应用程序时使用initial。一旦migrations文件夹包含一个名为0001_initial.py的文件，您就不再需要任何初始迁移。如果您从此更改表，请使用auto调用它，然后迁移：

./manage.py schemamigration myapp --auto
./manage.py migrate myapp