Python 从SQLAlchemy多对多删除匹配错误的行数

我尝试使用SQLAlchemy删除烧瓶中的多对多对象。我有这些模型，它们类似于：

但当我运行

commit

时，此操作失败：

db.session.commit()
2017-01-30 20:59:48,706 INFO sqlalchemy.engine.base.Engine DELETE FROM tags WHERE tags.tag_id = ? AND tags.document_id = ?
2017-01-30 20:59:48,706 INFO sqlalchemy.engine.base.Engine (2, 2)
2017-01-30 20:59:48,707 INFO sqlalchemy.engine.base.Engine ROLLBACK
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/scoping.py", line 157, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 874, in commit
    self.transaction.commit()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 461, in commit
    self._prepare_impl()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 441, in _prepare_impl
    self.session.flush()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2139, in flush
    self._flush(objects)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2259, in _flush
    transaction.rollback(_capture_exception=True)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
    raise value
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2223, in _flush
    flush_context.execute()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py", line 389, in execute
    rec.execute(self)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py", line 503, in execute
    self.dependency_processor.process_saves(uow, states)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py", line 1092, in process_saves
    secondary_update, secondary_delete)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py", line 1113, in _run_crud
    result.rowcount)
sqlalchemy.orm.exc.StaleDataError: DELETE statement on table 'tags' expected to delete 1 row(s); Only 5 were matched.

db.session.commit（）
2017-01-30 20:59:48706信息sqlalchemy.engine.base.engine从tags.tag_id=？和tags.document_id=？
2017-01-30 20:59:48706信息sqlalchemy.engine.base.engine（2,2）
2017-01-30 20:59:48707信息sqlalchemy.engine.base.engine回滚
回溯（最近一次呼叫最后一次）：
文件“”，第1行，在
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/scoping.py”，do中第157行
返回getattr（self.registry（），name）（*args，**kwargs）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，提交中的第874行
self.transaction.commit（）
提交中的文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，第461行
self.\u prepare\u impl（）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，第441行，在
self.session.flush（）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，第2139行，刷新
自冲洗（对象）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，第2259行，在\u flush中
事务.rollback（\u capture\u exception=True）
文件“/usr/lib/python3.6/site packages/sqlalchemy/util/langhelpers.py”，第60行，在退出时__
兼容性（exc_类型、exc_值、exc_tb）
文件“/usr/lib/python3.6/site packages/sqlalchemy/util/compat.py”，第187行，在reraise中
增值
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/session.py”，第2223行，在\u flush中
flush_context.execute（）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/unitofwork.py”，执行中第389行
rec.execute（self）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/unitofwork.py”，执行中的第503行
自相关性\u处理器。进程\u保存（uow，状态）
文件“/usr/lib/python3.6/site packages/sqlalchemy/orm/dependency.py”，第1092行，进程中保存
二次更新，二次删除）
文件“/usr/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py”，第1113行，在crud中
结果（行计数）
sqlalchemy.orm.exc.StaleDataError:表“tags”上的DELETE语句应删除1行；只有5个匹配。

如前所述，我们似乎有许多关联post标记。解决

tags = db.Table('tags',
    db.Column('tag_id', db.Integer, db.ForeignKey('tag.id')),
    db.Column('document_id', db.Integer, db.ForeignKey('document.id')),
    db.PrimaryKeyConstraint('tag_id', 'document_id')
)

---

相关文件：@piotrdawiduk谢谢，这似乎是合理的复制品。

db.PrimaryKeyConstraint

与

db.UniqueConstraint

相同，与

db.PrimaryKeyConstraint（'tag\u id'，'document\u id'）

中的

db.session.commit()
2017-01-30 20:59:48,706 INFO sqlalchemy.engine.base.Engine DELETE FROM tags WHERE tags.tag_id = ? AND tags.document_id = ?
2017-01-30 20:59:48,706 INFO sqlalchemy.engine.base.Engine (2, 2)
2017-01-30 20:59:48,707 INFO sqlalchemy.engine.base.Engine ROLLBACK
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/scoping.py", line 157, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 874, in commit
    self.transaction.commit()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 461, in commit
    self._prepare_impl()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 441, in _prepare_impl
    self.session.flush()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2139, in flush
    self._flush(objects)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2259, in _flush
    transaction.rollback(_capture_exception=True)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
    raise value
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/session.py", line 2223, in _flush
    flush_context.execute()
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py", line 389, in execute
    rec.execute(self)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py", line 503, in execute
    self.dependency_processor.process_saves(uow, states)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py", line 1092, in process_saves
    secondary_update, secondary_delete)
  File "/usr/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py", line 1113, in _run_crud
    result.rowcount)
sqlalchemy.orm.exc.StaleDataError: DELETE statement on table 'tags' expected to delete 1 row(s); Only 5 were matched.

tags = db.Table('tags',
    db.Column('tag_id', db.Integer, db.ForeignKey('tag.id')),
    db.Column('document_id', db.Integer, db.ForeignKey('document.id')),
    db.PrimaryKeyConstraint('tag_id', 'document_id')
)