SQLAlchemy DELETE：外键约束失败

Question

我有以下两张表：

class User(Base):
    __tablename__ = "user_entity"

    id = Column(String(32), primary_key=True, index=True)
    email = Column(String(32))
    email_constraint = Column(String(32))
    email_verified = Column(Boolean)
    enabled = Column(Boolean)
    federation_link = Column(String(32))
    first_name = Column(String(32))
    last_name = Column(String(32))
    realm_id = Column(String(32))
    username = Column(String(32))
    created_timestamp = Column(String(32))
    service_account_client_link = Column(String(32))
    not_before = Column(Integer)
    children = relationship("Userattribute", back_populates="parent")

class Userattribute(Base):
    __tablename__ = "user_attribute"

    name = Column(String(32))
    value = Column(String(32))
    id = Column(String(32), primary_key=True, index=True)
    user_id = Column(String(32), ForeignKey('user_entity.id', ondelete="CASCADE"))
    parent = relationship("User", back_populates="children")

我想通过他的 ID 从user_entity 表中删除一个用户：

[SQL: DELETE FROM user_entity WHERE user_entity.id = %s]

删除实现：

def delete_user(db: Session, id: str):
    return db.query(models.User).filter_by(id=id)

@app.delete("/entity/{id}", response_model=schemas.Userentity)
def del_user(id: str, db: Session = Depends(get_db)):
    user = crud.delete_user(db, id=id)
    user_obj = user.first()
    if user_obj is not None:
        user.delete()
        db.commit()
        return JSONResponse(content={"message": "user erfolgreich gelöscht"})
    else:
        raise HTTPException(status_code=400, detail=f"ID existiert nicht")

不幸的是，我收到以下错误：

 'Cannot delete or update a parent row: a foreign key constraint fails

为什么会失败？预期的行为是，当我删除用户时，user_attribute 表中的所有 user_attributes 也会被删除。如何解决？

Answer 1

我无法准确重现您的错误：user.delete() 引发 AttributeError。我想正确的电话应该是db.delete(user)。

---

删除行为也必须在父节点上的关系中指定：

children = relationship(
                "Userattribute",
                back_populates="parent",
                cascade="all, delete"
)

为了提高效率，您可能还想指定passive_deletes=True。

见Using foreign key ON DELETE cascade with ORM relationships。