SQLAlchemy 默认过滤器 [英] SQLAlchemy default filter

问题描述

我有一个带有 is_deleted 字段的模型，现在除了传递给 .filter 和 .filter_by 的任何过滤参数之外，我还希望该模型的所有查询形式始终通过 is_deleted=False 进行过滤.

I have a model with a field is_deleted, now I want all forms of query for this model to always filter by is_deleted=False in addition to whatever filtering arguments is passed to .filter and .filter_by.

在 Django 中，我通常会覆盖管理器并添加我自己的过滤器，但我需要 SQLAlchemy 的帮助.

In Django, I would normally override the manager and add my own filtering but I need help for SQLAlchemy.

更新:

我最终做了以下事情:

class CustomQuery(Query):
    def __new__(cls, *args, **kwargs):
        if args and hasattr(args[0][0], "is_deleted"):
            return Query(*args, **kwargs).filter_by(is_deleted=False)
        else:
            return object.__new__(cls)
session = scoped_session(sessionmaker(query_cls=CustomQuery))

它有效，但如果我稍后有更多字段，我想我将不得不添加更多条件，必须有一种方法可以在模型级别执行此操作.

It works but if I have more fields later on I imagine I'll have to add more condition, there must be a way to do this on the model level.

推荐答案

这是一个非常古老的问题，所以我确信 OP 解决了他们的问题，但由于它仍未得到解答(在 2021 年)这里是我们如何处理申请所有模型的自定义查询类:

This is a very old question so I'm sure the OP solved their issue, but as it remains unanswered (in 2021) here's how we've approached applying a custom query class to all models:

1. 如上定义自定义查询

class CustomQuery(Query): ...

1. 然后将此查询类设置为基本模型类的查询属性:

class BaseModel(Model):
    __abstract__ = True
    query_class = CustomQuery
    ...

那么任何实现 BaseModel 的模型显然都会继承这种行为:

Then any models implementing the BaseModel will obviously inherit this behaviour:

class MyModel(BaseModel):
    __tablename__ = 'my_model' 
    ....

请注意，在我们的示例中，并非所有表都遵循软删除模式(我们不关心每个表的历史记录).在这里，您可以实现一个使用默认查询类的单独 BaseModel.

Note, in our case not all of the tables follow the soft delete pattern (we don't care about the history of every single table). Here, you could implement a separate BaseModel that uses the default query class.

class ImmutableBaseModel(Model):
    __abstract__ = True
    query_class = CustomQuery
    ...

class MutableBaseModel(Model):
    __abstract__ = True

如果您发现自己在这里并且尚未阅读它，请查看 Miguel Grinberg 撰写的关于实施 软删除模式 和 伴随回购

If you find yourself here and you've not read it yet check out this excellent blog post from Miguel Grinberg on implementing the soft delete pattern and accompanying repo

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