mysql - 无法在 Django 1.11 中生成迁移

Question

在一个空白的 MySQL 数据库上，我使用以下命令为 Django 1.11 项目生成了迁移:

python manage.py makemigrations

我有几个自定义的相互依赖的应用程序，但生成的所有迁移都没有错误。但是，当我尝试应用这些迁移时:

python manage.py migrate

它可以很好地应用大多数应用程序迁移，但对于一些自定义 FeinCMS 迁移来说:

  Applying page.0001_initial...Traceback (most recent call last):
  File "manage.py", line 9, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 93, in __exit__
    self.execute(sql)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 101, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 205, in execute
    self.errorhandler(self, exc, value)
  File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')

不幸的是，它没有说明未生成哪个外键，并且迁移有多个外键。我尝试注释掉迁移中的每个字段并重新运行它，但是当我这样做时迁移会成功。

为什么此迁移失败以及如何修复它？

Answer 1

您在 Django 创建的表中遇到问题，该表没有 INNODB ENGINE。

在MySql中如果表有INNODB ENGINE可以将关系作为外键，否则Django将返回问题中提到的错误

"django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')"

我有解决这个问题的方法。首先创建新的管理命令文件，名称为“convert_to_innodb”

并在该管理命令文件中添加如下代码

from django.core.management.base import BaseCommand
from django.db import connections


class Command(BaseCommand):
    def handle(self, database="default", *args, **options):
        cursor = connections[database].cursor()
        cursor.execute("SHOW TABLE STATUS")
        for row in cursor.fetchall():
            if row[1] != "InnoDB":
                print "Converting %s" % row[0],
                print cursor.execute("ALTER TABLE %s ENGINE=INNODB" % row[0])

和终端中的 RUN 命令

python manage.py convert_to_innodb

执行此命令后，您可以在已创建的表中创建外键，但是

'OPTIONS': {
   'init_command': 'SET default_storage_engine=INNODB',
}

在数据库设置中添加此配置，如下所示

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql', 
        'NAME': 'DB_NAME',
        'USER': 'DB_USER',
        'PASSWORD': 'DB_PASSWORD',
        'HOST': 'localhost',   # Or an IP Address that your DB is hosted on
        'PORT': '3306',
        'OPTIONS': {
            'init_command': 'SET default_storage_engine=INNODB',
         }
    }
}

此数据库配置将创建下次 INNODB ENGINE 表，该表将在未来正常工作而不会出现错误