Question

根据某些DBMS的THIS问题，可以回滚CREATE TABLE语句。特别是sqlite是可能的（尽管它没有文档记录）。

所以我的问题是，是否可以在sqlalchemy中回滚create_all？我试图编写一些测试代码，但似乎不起作用：

>>> engine = create_engine('sqlite:///:memory:')
>>> engine
Engine(sqlite:///:memory:)
>>> Session = sessionmaker(bind=engine)
>>> connection = engine.connect()
>>> session = Session(bind=connection)
>>> engine.table_names()
[]
>>> transaction = connection.begin()
>>> Base = declarative_base()
>>> class Test(Base):
...    __tablename__ = 'TEST'
...    id = Column(Integer, primary_key=True)
...
>>> Base.metadata.bind = engine
>>> Base.metadata.create_all()
>>> engine.table_names()
[u'TEST']
>>> transaction.rollback()
>>> session.close()
>>> connection.close()
>>> engine.table_names()
[u'TEST']

Answer 1

使用Postgresql或SQL Server。 MySQL，Oracle不支持支持事务DDL。最近版本的SQLite似乎支持事务DDL。然而，Python sqlite3 driver does not。
简单的食谱：
```
with engine.begin() as conn:
    metadata.create_all(conn)
```
如果你在“with：”中引发异常，交易将被回滚。

想亲眼看看，好的：

from sqlalchemy import inspect   # need to be running 0.8 for this

with engine.connect() as conn:
   trans = conn.begin()
   metadata.create_all(conn)
   inspector = inspect(conn)
   table_names = inspector.get_table_names()
   trans.rollback()
   inspector = inspect(conn)
   rolled_back_table_names = inspector.get_table_names()

要了解交易范围，建议您阅读http://docs.sqlalchemy.org/en/latest/core/connections.html

是否可以在sqlalchemy中回滚create_all？

1 个答案: