在 Django 中同步多个数据库

Question

我以前在 Django 中拥有 SQLite 默认数据库，并将其用于用户身份验证。我正在构建一个 CMS，因此我需要存储图像。所以我在 settings.py 中添加了一个 PostgreSQL 数据库，并在 models.py 中为图像创建了新模型。如何将这些新更改迁移到新创建的数据库？如果我这样做了

python manage.py migrate

新创建的模型只会存储在 SQLite 数据库中，对吗？

Answer 1

你必须像这样在 settings.py 文件中指定你的数据库：

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
    'postgresql': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'myproject',
        'USER': 'myprojectuser',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '',
    }
}

然后，在您的项目文件夹中，您可以创建一个名为：routersGlobal.py

的文件

from django.conf import settings

class GlobalRouter(object):
    """
A router to control all database operations on models in the
auth application.
"""

    def db_for_read(self, model, **hints):
        """
        Attempts to read auth models go to auth.
        """
        app_list = ('auth', 'admin', 'contenttypes', 'sessions',)

        if model._meta.app_label in app_list:
            return 'default' #According to database name sqlite3
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write auth models go to auth.
        """
        app_list = ('auth', 'admin', 'contenttypes', 'sessions',)
        if model._meta.app_label in app_list:
            return 'default'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the auth app is involved.
        """
        app_list = ('auth', 'admin', 'contenttypes', 'sessions',)
        if obj1._meta.app_label in app_list and obj2._meta.app_label in app_list:
            return True
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Make sure the auth app only appears in the 'auth'
        database.
        """
        app_list = ('auth', 'admin', 'contenttypes', 'sessions',)

        if app_label in app_list:
            return db == 'default'
        return None

您可以创建一个名为 routersLocal.py 的文件：

from django.conf import settings

class LocalRouter(object):
    """
A router to control all database operations on models in the
auth application.
"""

    def db_for_read(self, model, **hints):
        """
        Attempts to read auth models go to auth.
        """
        app_list = ('YourNewApp',)

        if model._meta.app_label in app_list:
            return 'postgresql'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write auth models go to auth.
        """
        app_list = ('YourNewApp',)
        if model._meta.app_label in app_list:
            return 'postgresql'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the auth app is involved.
        """
        app_list = ('YourNewApp',)
        if obj1._meta.app_label in app_list and obj2._meta.app_label in app_list:
            return True
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """
        Make sure the auth app only appears in the 'auth'
        database.
        """
        app_list = ('YourNewApp',)

        if app_label in app_list:
            return db == 'postgresql'
        return None

最后在 settings.py 文件中你必须指定重定向：

DATABASE_ROUTERS = ['YourProjectName.routersLocal.LocalRouter', 'YourProjectName.routersGlobal.GlobalRouter']

然后，它应该可以工作并应用分离迁移