Python 在SqlAlchemy中将子类添加到会话时违反外键

我对目前的情况有所了解：

Base = declarative_base()

class Parent(Base):
    __tablename__ = 'parent'

    id = Column(String(32), primary_key=True, index=True)


class Child(Parent):
    __tablename__ = 'child'

    parent_id = Column(ForeignKey('parent.id'), primary_key=True)
    other_field = Column(String(32))


class Other(Base):
    __tablename__ = 'other'

    id = Column(String(32), primary_key=True, index=True)
    reference_to_parent = Column(ForeignKey('parent.id'), primary_key=True)


child = Child(id='some_id', other_field="blah")
session.add(child)

other = Other(id="some_other_id", reference_to_parent='some_id')
session.add(other)
session.commit()  # <-- sqlalchemy.exc.IntegrityError

但是，如果我这样做：

child = Child(id='id', other_field="blah")
session.add(child)
session.commit() . # <-- note the extra commit

other = Other(reference_to_parent='id')
session.add(other)
session.commit()

child=child（id='id'，other_field=“blah”）
会话.添加（子级）
session.commit（）。# 我认为您需要在第一次添加后添加一个
会话.flush（）
。Flush基本上会在挂起状态下将您的更改传递给数据库。Commit实际上会将它们写入数据库

child = Child(id='some_id', other_field="blah")
session.add(child)
session.flush()

other = Other(id="some_other_id", reference_to_parent='some_id')
session.add(other)
session.commit()

child = Child(id='some_id', other_field="blah")
session.add(child)
session.flush()

other = Other(id="some_other_id", reference_to_parent='some_id')
session.add(other)
session.commit()