使用 sqlalchemy 生成数据库表

Question

我目前正在尝试使用 sqlalchemy 库生成 SQL 表。

我有两个表：t_volume 和 t_volume_snapshot

class Volume(...):
    """ Represent a volume element"""

    __tablename__ = "t_volume"

    created_at = Column(DateTime, nullable=False)
    deleted_at = Column(DateTime, nullable=False)
    volume_id = Column(String(length=255), nullable=False, primary_key=True)
    volume_name = Column(String(length=255), nullable=False)
    volume_type = Column(String(length=255), nullable=False)
    volume_disk_space = Column(Integer, nullable=False)

class VolumeSnapshot(...):
    """ Represent a volume snapshot element"""

    __tablename__ = "t_volume_snapshot"

    created_at = Column(DateTime, nullable=False)
    deleted_at = Column(DateTime, nullable=False)
    volume_snapshot_id = Column(String(length=255), nullable=False, primary_key=True)
    volume_snapshot_name = Column(String(length=255), nullable=False)
    volume_id = Column(String(length=255), ForeignKey("t_volume.volume_id"))

我希望卷快照使用值 volume_id 引用卷。我试图将 t_volume_snapshot.volume_id 列定义为指向 t_volume.volume_id 的 ForeignKey，但我得到的只是

OperationalError: (OperationalError) (1005, "Can't create table 'db.t_volume_snapshot' (errno: 150)")

我一般不习惯 sqlalchemy 和 SQL，所以我可能遗漏了一些东西......

Answer 1

您应该能够执行以下操作

class Volume(...):
    """ Represent a volume element"""

    __tablename__ = "t_volume"

    created_at = Column(DateTime, nullable=False)
    deleted_at = Column(DateTime, nullable=False)
    volume_id = Column(String(length=255), nullable=False, primary_key=True)
    volume_name = Column(String(length=255), nullable=False)
    volume_type = Column(String(length=255), nullable=False)
    volume_disk_space = Column(Integer, nullable=False)

    snapshots = relationship("VolumeSnapshot", back_populates="t_volume")

class VolumeSnapshot(...):
    """ Represent a volume snapshot element"""

    __tablename__ = "t_volume_snapshot"

    created_at = Column(DateTime, nullable=False)
    deleted_at = Column(DateTime, nullable=False)
    volume_snapshot_id = Column(String(length=255), nullable=False, primary_key=True)
    volume_snapshot_name = Column(String(length=255), nullable=False)
    snapshot_volume_id = Column(String(length=255), ForeignKey("volume_id"))

这应该建立一个双向连接。