于小丘
209cb24ab4
- Implement PhysicalFile model to manage physical file references and reference counting. - Create Policy model with associated options and group links for storage policies. - Introduce Redeem and Report models for handling redeem codes and reports. - Add Settings model for site configuration and user settings management. - Develop Share model for sharing objects with unique codes and associated metadata. - Implement SourceLink model for managing download links associated with objects. - Create StoragePack model for managing user storage packages. - Add Tag model for user-defined tags with manual and automatic types. - Implement Task model for managing background tasks with status tracking. - Develop User model with comprehensive user management features including authentication. - Introduce UserAuthn model for managing WebAuthn credentials. - Create WebDAV model for managing WebDAV accounts associated with users.
91 lines
3.1 KiB
Python
91 lines
3.1 KiB
Python
"""
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乐观锁 Mixin
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提供基于 SQLAlchemy version_id_col 机制的乐观锁支持。
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乐观锁适用场景：
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- 涉及"状态转换"的表（如：待支付 -> 已支付）
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- 涉及"数值变动"的表（如：余额、库存）
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不适用场景：
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- 日志表、纯插入表、低价值统计表
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- 能用 UPDATE table SET col = col + 1 解决的简单计数问题
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使用示例：
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class Order(OptimisticLockMixin, UUIDTableBaseMixin, table=True):
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status: OrderStatusEnum
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amount: Decimal
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# save/update 时自动检查版本号
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# 如果版本号不匹配（其他事务已修改），会抛出 OptimisticLockError
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try:
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order = await order.save(session)
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except OptimisticLockError as e:
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# 处理冲突：重新查询并重试，或报错给用户
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l.warning(f"乐观锁冲突: {e}")
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"""
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from typing import ClassVar
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from sqlalchemy.orm.exc import StaleDataError
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class OptimisticLockError(Exception):
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"""
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乐观锁冲突异常
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当 save/update 操作检测到版本号不匹配时抛出。
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这意味着在读取和写入之间，其他事务已经修改了该记录。
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Attributes:
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model_class: 发生冲突的模型类名
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record_id: 记录 ID（如果可用）
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expected_version: 期望的版本号（如果可用）
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original_error: 原始的 StaleDataError
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"""
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def __init__(
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self,
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message: str,
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model_class: str | None = None,
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record_id: str | None = None,
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expected_version: int | None = None,
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original_error: StaleDataError | None = None,
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):
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super().__init__(message)
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self.model_class = model_class
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self.record_id = record_id
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self.expected_version = expected_version
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self.original_error = original_error
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class OptimisticLockMixin:
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"""
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乐观锁 Mixin
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使用 SQLAlchemy 的 version_id_col 机制实现乐观锁。
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每次 UPDATE 时自动检查并增加版本号，如果版本号不匹配（即其他事务已修改），
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session.commit() 会抛出 StaleDataError，被 save/update 方法捕获并转换为 OptimisticLockError。
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原理：
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1. 每条记录有一个 version 字段，初始值为 0
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2. 每次 UPDATE 时，SQLAlchemy 生成的 SQL 类似：
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UPDATE table SET ..., version = version + 1 WHERE id = ? AND version = ?
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3. 如果 WHERE 条件不匹配（version 已被其他事务修改），
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UPDATE 影响 0 行，SQLAlchemy 抛出 StaleDataError
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继承顺序：
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OptimisticLockMixin 必须放在 TableBaseMixin/UUIDTableBaseMixin 之前：
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class Order(OptimisticLockMixin, UUIDTableBaseMixin, table=True):
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...
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配套重试：
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如果加了乐观锁，业务层需要处理 OptimisticLockError：
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- 报错给用户："数据已被修改，请刷新后重试"
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- 自动重试：重新查询最新数据并再次尝试
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"""
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_has_optimistic_lock: ClassVar[bool] = True
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"""标记此类启用了乐观锁"""
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version: int = 0
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"""乐观锁版本号，每次更新自动递增"""
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