如何使用sqlalchemy中的關係更改父項？

Question

下面是與backref和刪除級聯關係的簡單示例。

class Parent(Base): 
    __tablename__ = 'parent' 
    id = Column(Integer, primary_key=True) 

class Child(Base): 
    __tablename__ = 'child' 
    id = Column(Integer, primary_key=True) 
    parent_id = Column(Integer, ForeignKey('Parent.id')) 
    parent = relation(
     'Parent', 
     backref=backref('children', cascade='delete, delete-orphan') 
    ) 

需要從一個父到另一個重新分配一些孩子，則需要刪除另一個父，但SQLAlchemy的父母刪除之前刪除的孩子......

p1 = Session.query(Parent).get(...) 
p2 = Session.query(Parent).get(...) 

p1.children.extend(p2.children) 
Session.delete(p2) 
Session.commit() 

登錄：

... [worker 0] UPDATE child SET parent_id=%(parent_id)s WHERE child.id = %(child_id)s 
... 
... [worker 0] DELETE FROM child WHERE child.id = %(id)s 
... 
... [worker 0] DELETE FROM parent WHERE parent.id = %(id)s 
... 
... [worker 0] COMMIT 

需要以某種方式將孩子從另一父母分離...

Answer 1

唯一的解決方案我可以建議的是：

p1 = Session.query(Parent).get(...) 
p2 = Session.query(Parent).get(...) 

for child in p2.children[:]: 
    child.parent = p1 

Session.delete(p2) 
Session.commit()