On Jan 26, 2011, at 5:45 PM, Michael Bayer wrote:
>
>
> From this it follows that if you'd like to emit several DDL statements in a
> transaction, the usage is no different for DDL expressions than for any other
> kind of DML statement (i.e insert/update/delete). Use
> connection.begin()/transaction.commit() as documented at:
>
> http://www.sqlalchemy.org/docs/core/connections.html#using-transactions
> .
>
> autocommit is described right after that:
>
>
> http://www.sqlalchemy.org/docs/core/connections.html#understanding-autocommit
>
> Also the public API for _execution_options is the execution_options()
> generative call:
>
>
> http://www.sqlalchemy.org/docs/core/expression_api.html?highlight=execution_options#sqlalchemy.sql.expression.Executable.execution_options
> .
Thanks for the prodding- I figured out my bug. Here is sample code that
demonstrates a little surprise.
First, this code that emits:
BEGIN (implicit)
SELECT 1
ROLLBACK
=========================
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
DDL("SELECT 1").execute(bind=session)
session.rollback()
=========================
and here is the buggy code which emits:
SELECT 1
COMMIT
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
DDL("SELECT 1").execute(bind=engine)
session.rollback()
=========================
Can you spot the difference? The DDL in the first code is bound to the session
and the latter code mistakenly binds to the engine for execution resulting in
two different execution paths. In hindsight, I guess it makes sense, but it
certainly was not easy to find...
Cheers,
M
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