在SQLAlchemy中，dict更新方法如何与ORM交互? [英] In SQLAlchemy, how does the dict update method interact with the ORM?

问题描述

所以我有一个带有JSON列的SQLAlchemy表:

So I had a SQLAlchemy Table with a JSON column:

from sqlalchemy.dialects.postgresql import JSON
class MyTable(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    my_json_column = db.Column(JSON)

我试图用dict#update方法更新列，如下所示:

And I tried to update the column with the dict#update method like so:

def foo(my_object, new_params):
    my_object.my_json_column.update(new_params)
    db.session.commit()

但是，那没有用.我的意思是，更新没有持久保存到数据库中.

起作用了，是这样的:

def foo(my_object, new_params):
    temp_params = my_object.my_json_column.copy()
    temp_params.update(new_params)
    my_object.my_json_column = new_params
    db.session.commit()

我怀疑这与不变性"有关，或者ORM仅注意到直接分配的更改等.有人知道为什么吗?

I suspect it has something to do with "immutability" or the ORM only notices changes on direct assignment, or something. Does anyone know exactly why?

推荐答案

是.默认情况下，SQLAlchemy不会跟踪内部 dict属性的更改.要使其跟踪更改，可以使用 mutable 扩展名:

Yes. By default SQLAlchemy doesn't track changes inside dict attributes. To make it track changes, you can use the mutable extension:

class MyTable(db.Model):
    ...
    my_json_column = db.Column(MutableDict.as_mutable(JSON))

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