django - 与django的manage.py脚本同步db时出现mysql异常

Question

我对 django 比较陌生。我已经定义了我的数据库模式并验证了它没有错误(manage.py 验证报告发现 0 个错误)。

但是当我运行 ./manage.pysyncdb

我得到以下堆栈跟踪:

Creating table demo_foobar_one
Creating table demo_foobar_two
<snip>...</snip>
Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_manager(settings)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/base.py", line 218, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/base.py", line 347, in handle
    return self.handle_noargs(**options)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/commands/syncdb.py", line 103, in handle_noargs
    emit_post_sync_signal(created_models, verbosity, interactive, db)
  File "/usr/local/lib/python2.6/dist-packages/django/core/management/sql.py", line 185, in emit_post_sync_signal
    interactive=interactive, db=db)
  File "/usr/local/lib/python2.6/dist-packages/django/dispatch/dispatcher.py", line 162, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/usr/local/lib/python2.6/dist-packages/django/contrib/auth/management/__init__.py", line 28, in create_permissions
    defaults={'name': name, 'content_type': ctype})
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 135, in get_or_create
    return self.get_query_set().get_or_create(**kwargs)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 373, in get_or_create
    obj.save(force_insert=True, using=self.db)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/base.py", line 435, in save
    self.save_base(using=using, force_insert=force_insert, force_update=force_update)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/base.py", line 528, in save_base
    result = manager._insert(values, return_id=update_pk, using=using)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 195, in _insert
    return insert_query(self.model, values, **kwargs)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 1479, in insert_query
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 783, in execute_sql
    cursor = super(SQLInsertCompiler, self).execute_sql(None)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 727, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.6/dist-packages/django/db/backends/util.py", line 15, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.6/dist-packages/django/db/backends/mysql/base.py", line 86, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/lib/python2.6/dist-packages/MySQL_python-1.2.3-py2.6-linux-i686.egg/MySQLdb/cursors.py", line 176, in execute
    if not self._defer_warnings: self._warning_check()
  File "/usr/local/lib/python2.6/dist-packages/MySQL_python-1.2.3-py2.6-linux-i686.egg/MySQLdb/cursors.py", line 92, in _warning_check
    warn(w[-1], self.Warning, 3)
_mysql_exceptions.Warning: Data truncated for column 'name' at row 1

我已经检查(并仔细检查)了我的表架构。所有name字段都是CharField类型，最大长度=64。我使用的后端数据库是MySQL，所以我确信可以为长度为64的字符串创建索引。

可能导致此错误的原因(我怀疑这是一个误导性的错误消息 - 即使它来自数据库本身)...

Answer 1

回溯是在创建 django.contrib.auth.Permission 期间发生的:其中一些是作为 syncdb 的一部分自动为您的模型创建的。

Permission.name 具有 max_length=50，因此您可能有一个名称很长的应用程序和/或模型类？

在 manage.py dbshel​​l 中尝试以下查询:

SELECT * FROM auth_permission WHERE LENGTH(name) = 50;

如果您无法更改模型名称，则可以通过在模型元类中指定 verbose_name 来减少生成的 Permission.name 的长度(请参阅 here 了解更多详细信息):

class MyVeryLongModelNameThatIsBreakingMyMigration(models.Model):
    class Meta:
        verbose_name = 'my long model'

更新

有一个开放的(截至 2013 年)Django 票证可以解决此问题:

• #8162 (Increase Permission.name max_length)