Question

当我尝试更新数据时，我的SQLAlchemy模型遇到了一些奇怪的行为。我有一个这样定义的一对多关系：

app = Flask(__name__)
app.config[
    "SQLALCHEMY_DATABASE_URI"
] = "postgresql://geonatadmin:monpassachanger@localhost:5432/geonature2db_test"
app.debug = True
DB = SQLAlchemy(app)


class Child(DB.Model):
    __tablename__ = "Child"

    id_child = DB.Column(DB.Integer, primary_key=True)
    id_parent = DB.Column(DB.Integer, ForeignKey("Parent.id_parent"))
    name = DB.Column(DB.Unicode(50))


class Parent(DB.Model):
    __tablename__ = "Parent"

    id_parent = DB.Column(DB.Integer, primary_key=True)
    name = DB.Column(DB.Unicode(50))

    childrens = relationship("Child", lazy="joined", cascade="all, delete-orphan")

DB.create_all()

我正在尝试从我的API发送的JSON更新Parent和Child。在我的示例中，一位父母已经有一个孩子，我尝试为其添加两个新孩子：

with app.app_context():
    first_json = {"name": "parent1", "childrens": [{"name": "john"}]}
    childrens = first_json.pop("childrens")
    parent = Parent(**first_json)
    for child in childrens:
        parent.childrens.append(Child(**child))

    DB.session.add(parent)
    DB.session.commit()
    DB.session.flush()

    second_json = {
        "id_parent": 1,
        "name": "parent1",
        "childrens": [
            {"id_child": 1, "name": "john"},
            {"id_child": None, "name": "foo"},
            {"id_child": None, "name": "bar"},
        ],
    }
    childrens = second_json.pop("childrens")
    parent = Parent(**second_json)
    for child in childrens:
        parent.childrens.append(Child(**child))

    DB.session.merge(parent)
    DB.session.commit()

最后，我的数据库中只有孩子1和孩子3。永远不会添加孩子2。

我试图获取有关此配置发出的实际SQL的更多信息：

current_app.config["SQLALCHEMY_ECHO"] = True

并且确实没有针对Child 2的INSERT语句。

Answer 1

我最终发现，如果删除“ id_child”为“无”，则合并工作正常。像这样：

second_json = {
    "id_parent": 1,
    "name": "parent1",
    "childrens": [
        {"id_child": 1, "name": "john"},
        {"name": "foo"},
        {"name": "bar"},
    ],
}

与包含的相关对象合并时，不会保留新的关系

1 个答案: