django-south - 南和不能 DROP 'created_date' ;检查列/键是否存在”

Question

我尝试添加我的模型 Markdown ，但出现错误。
我的旧models.py:

class Post(models.Model):
    title = models.CharField(max_length=255)
    slug = models.SlugField(max_length=255, unique=True)
    excerpt = models.TextField(blank=True, help_text="A small teaser of\
                your content")
    content = models.TextField()
    date_created = models.DateTimeField(auto_now_add=True)
    is_published = models.BooleanField(default=True)
    objects = models.Manager()
    published_objects = PublishedManager()
    tags = TaggableManager()
category = models.ForeignKey(Category)

和我的新models.py

class Post(models.Model):
    title = models.CharField(max_length=255)
    slug = models.SlugField(max_length=255, unique=True)
    excerpt = models.TextField(blank=True, help_text="A small teaser of\
                your content")
    content = models.TextField()
    contentmarkdown = models.TextField()
    date_created = models.DateTimeField(auto_now_add=True)
    is_published = models.BooleanField(default=True)
    objects = models.Manager()
    published_objects = PublishedManager()
    tags = TaggableManager()
    category = models.ForeignKey(Category)

    def save(self):
        self.content = markdown.markdown(self.contentmarkdown)
        super(Post, self).save() # Call the "real" save() method.

当我使用南和这一行之后:python manage.py migrate blog
我收到此错误:

File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 443, in execute_from_command_line
    utility.execute()
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 382, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py", line 196, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/core/management/base.py", line 232, in execute
    output = self.handle(*args, **options)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/management/commands/migrate.py", line 108, in handle
    ignore_ghosts = ignore_ghosts,
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/__init__.py", line 213, in migrate_app
    success = migrator.migrate_many(target, workplan, database)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 235, in migrate_many
    result = migrator.__class__.migrate_many(migrator, target, migrations, database)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 310, in migrate_many
    result = self.migrate(migration, database)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 133, in migrate
    result = self.run(migration)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 107, in run
    return self.run_migration(migration)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 81, in run_migration
    migration_function()
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/migration/migrators.py", line 57, in <lambda>
    return (lambda: direction(orm))
  File "/home/ada/mainproject/blog/migrations/0004_auto__del_field_book_created_date__add_field_post_contentmarkdown__chg.py", line 12, in forwards
    db.delete_column('blog_book', 'created_date')
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/db/mysql.py", line 28, in _column_rm
    return func(self, table_name, column_name, *args, **opts)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/db/mysql.py", line 217, in delete_column
    super(DatabaseOperations, self).delete_column(table_name, name)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/db/generic.py", line 51, in _column_rm
    return func(self, table, column, *args, **opts)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/db/generic.py", line 886, in delete_column
    self.execute(self.delete_column_string % params, [])
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/south/db/generic.py", line 273, in execute
    cursor.execute(sql, params)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/db/backends/util.py", line 40, in execute
    return self.cursor.execute(sql, params)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 114, in execute
    return self.cursor.execute(query, args)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 201, in execute
    self.errorhandler(self, exc, value)
  File "/home/ada/virtualenv/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
django.db.utils.DatabaseError: (1091, "Can't DROP 'created_date'; check that column/key exists")

请你告诉我为什么我会收到这个错误？ 'created_date' 没有任何意义？？

Answer 1

这是因为您正在尝试删除包含“created_date”列的内容，如果您查看错误，它指的是文件、行号，甚至是有问题的代码片段。

File "/home/ada/mainproject/blog/migrations/0004_auto__del_field_book_created_date__add_field_post_contentmarkdown__chg.py", line 12, in forwards db.delete_column('blog_book', 'created_date')

当您在变量“date_created”和“created_date”之间切换时，您似乎指的是错误的列名