使用 South (django) 和 MySQL 进行架构迁移

Question

我刚刚完成了 django 教程，并且遵循了每一步，但每次尝试迁移时仍然会出现此错误：

初始迁移有效，但尝试迁移它，我得到了：

  root@debian:/Sites/tumblog# ./manage.py migrate blog

   Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_manager(settings)
  File "/usr/lib/pymodules/python2.6/django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "/usr/lib/pymodules/python2.6/django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/pymodules/python2.6/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/pymodules/python2.6/django/core/management/base.py", line 220, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/pymodules/python2.6/south/management/commands/migrate.py", line 102, in handle
    delete_ghosts = delete_ghosts,
  File "/usr/lib/pymodules/python2.6/south/migration/__init__.py", line 202, in migrate_app
    success = migrator.migrate_many(target, workplan, database)
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 215, in migrate_many
    result = migrator.__class__.migrate_many(migrator, target, migrations, database)
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 284, in migrate_many
    result = self.migrate(migration, database)
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 121, in migrate
    result = self.run(migration)
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 95, in run
    return self.run_migration(migration)
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 77, in run_migration
    migration_function()
  File "/usr/lib/pymodules/python2.6/south/migration/migrators.py", line 56, in <lambda>
    return (lambda: direction(orm))
  File "/Site/tumblog/blog/migrations/0005_initial.py", line 17, in forwards
    ('name', self.gf('django.db.models.fields.CharField')(max_length=255)),
  File "/usr/lib/pymodules/python2.6/south/db/generic.py", line 210, in create_table
    ', '.join([col for col in columns if col]),
  File "/usr/lib/pymodules/python2.6/south/db/generic.py", line 134, in execute
    cursor.execute(sql, params)
  File "/usr/lib/pymodules/python2.6/django/db/backends/util.py", line 15, in execute
    return self.cursor.execute(sql, params)
  File "/usr/lib/pymodules/python2.6/django/db/backends/mysql/base.py", line 86, in execute
    return self.cursor.execute(query, args)
  File "/usr/lib/pymodules/python2.6/MySQLdb/cursors.py", line 166, in execute
    self.errorhandler(self, exc, value)
  File "/usr/lib/pymodules/python2.6/MySQLdb/connections.py", line 35, in defaulterrorhandler
    raise errorclass, errorvalue
_mysql_exceptions.OperationalError: (1050, "Table 'blog_blog' already exists")

我已经四处搜索并发现添加 --fake 会跳过这个错误，但它不会改变什么？这里有什么问题以及如何解决它？

Answer 1

您确定添加 --fake 不会改变任何东西吗？

manage.py migrate blog --fake

...或从 mysql 控制台手动删除表“blog_blog”;)

Answer 2

问题是迁移尝试创建的表已存在于数据库中。它们必须是使用syncdb创建的（如果您执行syncdb并稍后开始为应用程序使用south，您会得到这个），或者通过之前的迁移创建。

迁移名称 0005_initial 很可疑。迁移 0001-0004 在做什么？

要解决您的问题，您应该首先确保没有重复的迁移（例如，0001_initial 创建表，然后 0005_initial 尝试再次执行此操作）。您只需要对应用程序进行一次初始迁移，接下来的迁移应该只记录对架构的更改。

然后，从数据库中删除表并再次创建它们。类似的方法可能会起作用：

./manage.py migrate [appname] --fake
./manage.py migrate [appname] zero
./manage.py migrate [appname]

如果失败（如果迁移中同时存在现有表和新表，则会失败）-那么您必须在 mysql 控制台中手动删除表。

Answer 3

您的迁移中实际发生了什么？如果您收到此错误，则只需为 blog_blog 调用 create_table 两次，或者在初始迁移之前数据库中已存在 blog_blog（可能是，这是之前尝试创建博客的剩余部分，但从未迁移到零）。

如果错误发生在初始迁移完成之前，那么它很可能是一个工件，您可以手动将其从数据库中删除，然后重试。如果初始迁移成功，但后来的迁移失败，则查找 blog_blog 的重复 create_table 位置。