迁移失败并出现警告“'utf8' 当前是字符集 UTF8MB3 的别名，但在未来版本中将是 UTF8MB4 的别名”

Question

在我的 Django 项目中，我试图将数据库字段从 OneToOne 更改为 ForeignKey。当我运行“python manage.py migrate”时，它会以一个很长的回溯中断，并以我在标题中引用的警告结尾。我知道其他人遇到了这个问题，但我找不到解决方案。

我已将以下内容添加到我的 local_settings.py 数据库中：

'OPTIONS': {
            'autocommit': True,
            'charset': 'utf8mb4',  
           }

起初我尝试简单地将 OneToOne 更改为 ForeignKey，但遇到了这个问题。因此，我决定分步执行，首先删除该字段，然后将其添加为新的字段类型。但我什至无法删除该字段。

这是由 makemigrations 生成的迁移文件，是迁移中断的文件：

# Generated by Django 2.2.3 on 2019-07-18 09:59

from django.db import migrations


class Migration(migrations.Migration):

    dependencies = [
        ('sweaters', '0011_auto_20190718_0954'),
    ]

    operations = [
        migrations.RemoveField(
            model_name='sweater',
            name='yarn_for',
        ),
    ]

这是我得到的完整回溯：

$ python manage.py migrate
Operations to perform:
  Apply all migrations: account, admin, auth, contenttypes, sessions, sweaters
Running migrations:
  Applying sweaters.0012_remove_sweater_yarn_for...Traceback (most recent call last):
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/utils.py", line 96, in inner
    return func(*args, **kwargs)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/mysql/connector/cursor.py", line 897, in fetchall
    self._handle_eof(eof)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/mysql/connector/cursor.py", line 838, in _handle_eof
    self._warnings[0][1], self._warnings[0][2])
mysql.connector.errors.DatabaseError: 3719: 'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/core/management/commands/migrate.py", line 234, in handle
    fake_initial=fake_initial,
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/migrations/executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/migrations/executor.py", line 245, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/migrations/migration.py", line 124, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/migrations/operations/fields.py", line 178, in database_forwards
    schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 479, in remove_field
    fk_names = self._constraint_names(model, [field.column], foreign_key=True)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 1115, in _constraint_names
    constraints = self.connection.introspection.get_constraints(cursor, model._meta.db_table)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/mysql/connector/django/introspection.py", line 320, in get_constraints
    for constraint, column, ref_table, ref_column in cursor.fetchall():
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/utils.py", line 96, in inner
    return func(*args, **kwargs)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/django/db/utils.py", line 96, in inner
    return func(*args, **kwargs)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/mysql/connector/cursor.py", line 897, in fetchall
    self._handle_eof(eof)
  File "/Users/frankjernigan/Documents/webdev/phrancko-web-dev/phrancko.com/phrancko-project/myenv/lib/python3.7/site-packages/mysql/connector/cursor.py", line 838, in _handle_eof
    self._warnings[0][1], self._warnings[0][2])
django.db.utils.DatabaseError: (3719, "3719: 'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.", None)

Answer 1

这是 MySQL 切换默认设置的问题，mysql-connector-python 不是最新的。此处提供了一种解决方法：

https://code.djangoproject.com/ticket/29678

您使用的是哪个版本的mysql-connector-python？我想知道它是否可能已通过链接中的解决方法在更新的版本中进行了修补。