Magnus Hult ha scritto:

Thanks for your swift reply!

On 6/13/07, Manlio Perillo wrote:

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Magnus Hult ha scritto:

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When executing the following program, changes in the database (other than those made by this program) aren't visible until it is restarted, due to some form of SQLAlchemy caching:

Are you using PostgreSQL?

Yes, I am. With psycopg2.

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[...] The solution is: make sure to add a commit after every select.

It doesn't seem to help though. In fact, the following little program

t = objectstore.create_transaction() m = model.MyModel.get(1) print m.some_column t.commit() sys.stdin.readline() t = objectstore.create_transaction() m = model.MyModel.get(1) print m.some_column t.commit()

only seems to execute one select statement. The other result seems to be taken from the cache. If this is the case, then this question would rather belong in an SQLAlchemy mailing list, I guess.

The problem can be this: http://www.sqlalchemy.org/docs/documentation.html#unitofwork_identitymap After the first "select" you do not reset the Unif Of Work. In my queries I always do: def _sessionTransaction(self, callable_, *args, **kwargs): from sqlalchemy import orm conn = self.contextual_connect() sess = orm.create_session(bind_to=conn) # This cannot fail try: trans = sess.create_transaction() try: ret = callable_(conn, sess, *args, **kwargs) trans.commit() return ret except: trans.rollback() raise finally: sess.close() # This cannot fail conn.close() I create and close a new session object for every request. You can give a look at my nadbapi: http://developer.berlios.de/projects/nadbapi/ Regards Manlio Perillo

only seems to execute one select statement. The other result seems to be taken from the cache.

AFAIK, SQLAlchemy does perform the select statements, but, the second time, does not populate your mapped object since it's already present in the identity_map cache. You can see these by turning SA's engine.echo = True

Yes, that seems to be the problem. For this my tiny problem, I can get away by simply not using activemapper, though.

Have you tried myobject.refresh(), before the second time ? This will force SA to repopulate your instance Also, depending on your application behavior, you might want to consider a request to your server <=> a session in SA (that's usually what used for web apps). This means each time you end a request, you would have to session.clear(), preventing any caching. Hope that helps. Cheers, Seb -- Sébastien LELONG http://sirloon.net http://sirbot.org sebastien.lelong[at]sirloon.net

On 6/13/07, Colin Alston wrote:

On 13/06/2007 15:56 Magnus Hult wrote:

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only seems to execute one select statement. The other result seems to be taken from the cache. If this is the case, then this question would rather belong in an SQLAlchemy mailing list, I guess.

Have you tried using the sAsync wrapper for Twisted? I have not experienced caching problems with anything wrapped with it's transaction decorator.

No, I stumbled upon it while investigating this problem though. I'll definitely give it a closer look!