python - 在 RedShift 中使用 Django 多数据库

Question

我正在尝试使用 Django 多数据库配置，将 MYSQL 作为我的默认数据库，将 redshift 作为我的分析数据库。我的配置有时看起来像这样:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'xxxx',
        'USER': 'xxxx',
        'PASSWORD': 'xxxx',
        'HOST': 'localhost',
    },
    'analytics': {
        'NAME': 'analytics',
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'USER': 'XXXXXXXXX',
        'PASSWORD': 'XXXXX',
        'HOST': 'XXXXX.us-east-1.redshift.amazonaws.com',
        'PORT': 5439,
    }
}

当我尝试使用以下命令迁移我的分析应用程序时

python manage.py migrate analytics --database analytics

我看到以下错误:

  File "/opt/envs/cinematique/bin/django-admin.py", line 5, in <module>
    management.execute_from_command_line()
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/base.py", line 338, in execute
    output = self.handle(*args, **options)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 60, in handle
    return self.show_migration_list(connection, args)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 308, in show_migration_list
    loader = MigrationLoader(connection, ignore_no_migrations=True)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/migrations/loader.py", line 48, in __init__
    self.build_graph()
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/migrations/loader.py", line 183, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/migrations/recorder.py", line 59, in applied_migrations
    self.ensure_schema()
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/migrations/recorder.py", line 53, in ensure_schema
    editor.create_model(self.Migration)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/backends/schema.py", line 270, in create_model
    self.execute(sql, params)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/backends/schema.py", line 111, in execute
    cursor.execute(sql, params)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/opt/envs/cinematique/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.NotSupportedError: Column "django_migrations.id" has unsupported type "serial".

关于如何解决这个问题有什么想法吗？我正在使用 Django==1.7.9 和 psycopg2==2.6.1

Answer 1

具体问题是:Django 想创建一个带有serial 主键的迁移管理表来跟踪迁移历史。 Redshift 不支持。

不过，该方法更普遍的问题是，您并不真的希望在 Redshift 数据库上进行 Django 风格的迁移(参见 How to change table schema after created in Redshift? 之类的内容)。 Redshift 适用于大型数据库，更改其模式可能是一项重量级的工作。

所以，答案是:不要将 Django 迁移与 redshift 一起使用。 Syncdb 可能没问题，可以初始化您的表，但之后您将需要手动管理模式。不要在其模型适用于 Redshift 的应用程序中创建 migrations__init__.py 文件。

此处的相关/重复问题:

• Column 'django_migrations.id' has unsupported type 'serial' [ with Amazon Redshift]
• Error : django_migrations.id has unsupported type "serial" with Amazon Redshift