如何将数据库路由器添加到 Django 项目

Question

我正在按照此处的有关如何在一个 Django 项目中处理多个数据库的说明进行操作 topics/db/multi-db

我已经创建了所需的两个路由器。它们被保存为 ./database_routers/discourse.py 和 ./database_routers/wordpress.py

./database_routers/discourse.py的内容是

class DiscourseRouter:
    """
    A router to control all database operations on models in the
    discourse application.
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read discourse models go to discourse.
        """
        if model._meta.app_label == 'discourse':
            return 'discourse'
        return None

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

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

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the discourse app only appears in the 'discourse'
        database.
        """
        if app_label == 'discourse':
            return db == 'discourse'
        return None

./database_routers/wordpress.py的内容是

class WordpressRouter:
    """
    A router to control all database operations on models in the
    wordpress application.
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read wordpress models go to wordpress.
        """
        if model._meta.app_label == 'wordpress':
            return 'wordpress'
        return None

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

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

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        Make sure the wordpress app only appears in the 'wordpress'
        database.
        """
        if app_label == 'wordpress':
            return db == 'wordpress'
        return None

我创建了一个空的 ./database_routers/__init__.py 文件

api/settings中的数据库路由器设置我已经设置为

DATABASE_ROUTERS = ['database_routers.DiscourseRouter', 'database_routers.WordpressRouter']

当我尝试使用 shell 加上我使用

查看项目时

 ./manage.py shell_plus

我明白了

ImportError: Module "database_routers" does not define a "DiscourseRouter" attribute/class

如何将数据库路由器添加到 Django 项目，以便 python 识别路径 directory_name.ClassName？

Answer 1

如果我很了解你，你打算配置多个数据库对吗？请在下面找到：

class ExampleDatabaseRouter(object):
    """
    Determine how to route database calls for an app's models (in this case, for an app named Example).
    All other models will be routed to the next router in the DATABASE_ROUTERS setting if applicable,
    or otherwise to the default database.
    """

    def db_for_read(self, model, **hints):
        """Send all read operations on Example app models to `example_db`."""
        if model._meta.app_label == 'example':
            return 'example_db'
        return None

    def db_for_write(self, model, **hints):
        """Send all write operations on Example app models to `example_db`."""
        if model._meta.app_label == 'example':
            return 'example_db'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """Determine if relationship is allowed between two objects."""

        # Allow any relation between two models that are both in the Example app.
        if obj1._meta.app_label == 'example' and obj2._meta.app_label == 'example':
            return True
        # No opinion if neither object is in the Example app (defer to default or other routers).
        elif 'example' not in [obj1._meta.app_label, obj2._meta.app_label]:
            return None

        # Block relationship if one object is in the Example app and the other isn't.
            return False

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """Ensure that the Example app's models get created on the right database."""
        if app_label == 'example':
            # The Example app should be migrated only on the example_db database.
            return db == 'example_db'
        elif db == 'example_db':
            # Ensure that all other apps don't get migrated on the example_db database.
            return False

        # No opinion for all other scenarios
        return None

您也可以从 enter link description here

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Answer 2

您遗漏了模块名称。

DATABASE_ROUTERS = [
    'database_routers.discourse.DiscourseRouter', 
    'database_routers.wordpress.WordpressRouter'
]

Answer 3

除了 Daniel 的回答之外，另一个让您有更多控制权的选择是在 __init__ 中声明您的类。

database_routers.__init__.py 的内容：

from .discourse.DiscourseRouter
from .wordpress.WordpressRouter


__all__ = [
    "DiscourseRouter",
    "WordpressRouter",
]

然后这允许您删除 settings.py:

中的模块名称

DATABASE_ROUTERS = [
    'database_routers.DiscourseRouter', 
    'database_routers.WordpressRouter'
]

换句话说，原始代码可以工作。

这可以让您更好地控制哪些模块是 public。

注意：这个 __init__.py / __all__ 模式被广泛使用，例如：https://github.com/django/django/blob/master/django/db/init.py

如何将数据库路由器添加到 Django 项目

How to add database routers to a Django project

python

django

module

django-database