Hang in Python script using SQLAlchemy and multiprocessing

Question

Consider the following Python script, which uses SQLAlchemy and the Python multiprocessing module. This is with Python 2.6.6-8+b1(default) and SQLAlchemy 0.6.3-3 (default)

Answer 1

The TypeError: ('__init__() takes at least 4 arguments (2 given) error isn't related to the sql you're trying to execute, it has to do with how you're using SqlAlchemy's API.

The trouble is that you're trying to call execute on the session class rather than an instance of that session.

Try this:

session = Session()
session.execute("COMMIT; BEGIN; TRUNCATE foo%s; COMMIT;")
session.commit()

From the docs:

It is intended that the sessionmaker() function be called within the global scope of an application, and the returned class be made available to the rest of the application as the single class used to instantiate sessions.

So Session = sessionmaker() returns a new session class and session = Session() returns an instance of that class which you can then call execute on.