带有多个数据库的Django迁移

问题描述

我很难创建数据迁移。我的应用程序使用两个数据库。我在settings.py中配置了数据库，并在Django 。

I have a hard time with creating data migrations. I use two databases for my apps. I configured databases in settings.py and also created a router like in Django docs.

# settings.py
DB_HOST = 'localhost'
DATABASES = {
'default': {
    'ENGINE': 'django.db.backends.mysql',
    'NAME': 'helios',
    'HOST': DB_HOST,
    'OPTIONS': {
        'read_default_file': join(dirname(__file__), 'default.cnf'),
    },
},
'other': {
    'ENGINE': 'django.db.backends.mysql',
    'NAME': 'gala_pol',
    'HOST': DB_HOST,
    'OPTIONS': {
        'read_default_file': join(dirname(__file__), 'other.cnf'),
    },
},

DATABASE_APPS_MAPPING = {
    'contenttypes': 'default',
    'auth': 'default',
    'admin': 'default',
    'sessions': 'default',
    'messages': 'default',
    'staticfiles': 'default',
    'woodsmen': 'default',
    'helios': 'default',
    'hush': 'default',
    'hunt': 'other',
    'meat': 'other',
    'beast': 'other',
}

# routers.py

class DatabaseAppsRouter(object):

    def db_for_read(self, model, **hints):

        if model._meta.app_label in settings.DATABASE_APPS_MAPPING:
            return settings.DATABASE_APPS_MAPPING[model._meta.app_label]
        return None

    def db_for_write(self, model, **hints):

        if model._meta.app_label in settings.
            return settings.DATABASE_APPS_MAPPING[model._meta.app_label]
        return None

    def allow_relation(self, obj1, obj2, **hints):

        db1 = settings.DATABASE_APPS_MAPPING.get(obj1._meta.app_label)
        db2 = settings.DATABASE_APPS_MAPPING.get(obj2._meta.app_label)
        if db1 and db2:
            return db1 == db2
        return None

    def allow_migrate(self, db, app_label, model_name=None, **hints):

        if db in settings.DATABASE_APPS_MAPPING.values():
            return settings.DATABASE_APPS_MAPPING.get(app_label) == db
    elif app_label in settings.DATABASE_APPS_MAPPING:
            return False

以下是其中一个应用程序的模型和迁移：

Here is the model and migrations of one of those apps:

# hunt.models.py

class Dish(models.Model):
    """
    Investigation case
    """
    display_name = models.CharField(max_length=64, unique=True)
    department = models.ForeignKey(Kitchen, null=True)
    case_type = models.PositiveSmallIntegerField(choices=CASE_TYPE_CHOICES, default=DEF_CASE_TYPE)
    created_at = models.DateTimeField(blank=True, null=True)
    comment = models.CharField(max_length=256, blank=True, null=True)

    class Meta:
        verbose_name = 'case'
        app_label = 'hunt'

    def __unicode__(self):
        return (u'%s (%s)' % (self.display_name, self.created_at)).strip()


# hunt.migrations.0001_initial.py

class Migration(migrations.Migration):

    app_label = 'hunt'

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Dish',
            fields=[
                ('id', models.AutoField(verbose_name='ID', auto_created=True, primary_key=True, serialize=False)),
                ('display_name', models.CharField(max_length=64, unique=True)),
                ('case_type', models.PositiveSmallIntegerField(default=0, choices=[(0, 'Unknown'), (1, 'General'), (2, 'Terror'), (3, 'Narco'), (4, 'Fraud'), (5, 'Slavery'), (6, 'Traffic'), (7, 'RICO'), (8, 'War'), (9, 'Cyber'), (20, 'Other')])),
                ('created_at', models.DateTimeField(null=True, blank=True)),
                ('comment', models.CharField(max_length=256, null=True, blank=True)),
            ],
            options={
                'verbose_name': 'case',
            },
        ),
    ]

# hunt.migrations.0002_add_hunts.py


def create_initial_hunts(apps, schema_editor):

    if settings.DEBUG:
        print('\nContent added')


class Migration(migrations.Migration):
    dependencies = [
        ('hunt', '0001_initial'),
    ]


    operations = [
        migrations.RunPython(create_initial_hunts, hints={'schema_editor': 'other'}),
    ]

The问题是：
当我运行 migrate命令时，仅连接到默认数据库的应用程序会被迁移。其余应用程序的迁移将永远不会运行。如果我使用--database选项为此类应用启动迁移-则可以正常工作。

The problem is: When i run "migrate" command, only applications that connected to default database are migrated. The migrations in rest of the apps are never run. If I launch migrate for such an app with --database option - it works fine.

如何为每次迁移指定数据库？路由器不应该完全管理吗？还是我错过了其他东西？

How can I specify the database per migration? Isn't the router supposed to manage exactly this? Or I missed something else?

推荐答案

您为每个数据库运行一次迁移，指定具有-数据库的目标。每次它将咨询您的路由器以查看在该数据库上实际执行哪些迁移。

You have to run migrate once for each database, specifying the target with --database. Each time it will consult your router to see which migrations to actually perform on that database.

我猜它的设计方式是使显性胜于隐性。例如，您的工作流程可能要求您在不同的时间迁移不同的数据库。

I'm guessing it was designed this way to favor explicitness over implicitness. For example, your workflow might require you to migrate the different databases at different times.

但是请注意，您将无法从输出中得知实际执行了哪些迁移， ：

Note, though, that you won't be able to tell from the output which migrations were actually performed, since:

这篇关于带有多个数据库的Django迁移的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！