在 SQLAlchemy 中插入带有外键的对象的正确方法是什么? [英] What is the proper way to insert an object with a foreign key in SQLAlchemy?

问题描述

在使用 SQLAlchemy 时，将对象插入具有外键列的表然后提交它的理想方法是什么?在下面的代码中插入带有外来的对象有什么问题吗?

When using SQLAlchemy, what is the ideal way to insert an object into a table with a column that is a foreign key and then commit it? Is there anything wrong with inserting objects with a foreign in the code below?

def retrieve_objects():
    session = DBSession()
    return session.query(SomeClass).all()

def insert_objects():
    session = DBSession()
    for obj in retrieve_objects():
        another_obj = AnotherClass(somefield=0)
        obj.someforeignkey = another_obj
        session.add(obj)
    session.flush()
    transaction.commit()
    session.close()
    return None

推荐答案

如果您没有在 ORM 对象上使用 SQLAlchemy 关系，则必须手动处理外键.这意味着您必须首先创建父对象，从数据库中取回其主键，然后在子对象的外键中使用该键:

If you aren't using SQLAlchemy relationships on your ORM objects you have to manually deal with foreign keys. This means you have to create the parent object first, get its primary key back from the database, and use that key in the child's foreign key:

def retrieve_objects():
    session = DBSession()
    return session.query(SomeClass).all()

def insert_objects():
    session = DBSession()
    for obj in retrieve_objects():
        another_obj = AnotherClass(somefield=0)
        session.add(another_obj)
        session.flush() # generates the pkey for 'another_obj'
        obj.someforeignkey = another_obj.id # where id is the pkey
        session.add(obj)
    transaction.commit()

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