connections are generally not held onto anywhere; so connection-using operations are usually threadsafe. the only time a connection is held onto somewhere is when you explicitly hold onto a Connection yourself, or a Transaction, or a SessionTransaction. A SessionTransaction occurs during a session.flush() as well, so Sessions are not connection-threadsafe when used with flush(). if you use a thread-local SessionContext, you should be fine in that regard.
Also, objects loaded by a Session may have some lazy-loaders present on them which also can initiate connection-using operations, so that is something to be aware of. if you have objects with unexecuted lazy loaders that are going to be shared among threads, you might want to make sure they dont remain within a session that is going to be used for flush() operations. On Jun 21, 2006, at 4:51 PM, Randall Smith wrote: > I too am using sqlalchemy 0.2 with turbogears. I've been looking > at the > docs, but I lose my understanding of what's happening with connections > when going through the connection->engine->session abstractions. > > What's a good approach to using sqlalchemy in a threaded > environment so > that I can avoid thread safety issues with connections? I'd prefer to > not rely on the database driver's thread safety features. > > Randall > > Michael Bayer wrote: >> jonathan - >> >> it all changes for the better in 0.2. forget about >> objectstore.begin (). >> >> check it out at: http://www.sqlalchemy.org/docs_02/ >> >> >> On May 11, 2006, at 8:43 PM, Jonathan Vanasco wrote: >> >>> >>> i'm using sqlalchemy through turbogears >>> >>> turbogears doesn't have all-that-hot support for sqlalchemy yet, >>> and >>> I can't stand its user visit/identity system, so i'm >>> implementing my >>> own (sorry Kevin) >>> >>> i've come up with the following way to handle what I want to do via >>> the cherrypy request phases >>> >>> before_request_body >>> use sqlalchemy to load a session obj >>> >>> =snip >>> >>> on_end_resource >>> update the session object and commit >>> >>> my problem is that where i snipped things in the middle, turbogears >>> does some stuff itself, i'm guessing there's a begin/commit or >>> something in there... and i wind up with this error >>> === >>> File "build/bdist.darwin-8.6.0-Power_Macintosh/egg/sqlalchemy/ >>> mapping/unitofwork.py", line 147, in _validate_obj >>> InvalidRequestError: Detected a mapped object not present in the >>> current thread's Identity Map: '(<class 'myapp.model.Class'>, >>> ('62dd49990089f0c3c4e57ff54984e55ec90ffa6e',), None)'. Use >>> objectstore.import_instance() to place deserialized instances or >>> instances from other threads >>> === >>> >>> would anyone have a suggestion on how i can 'check out' a unit of >>> work and force it to persist? >>> >>> I tried calling objectstore.begin() , hoping things would >>> nest -- >>> no luck >>> >>> i tried creating explicit sessions using objectstore.Session -- >>> also no luck >>> >>> this might be impossible, i fear. but i'm hoping for the best. >>> >>> >>> >>> >>> | - - - - - - - - - - - - - - - - - - - - >>> | RoadSound.com / Indie-Rock.net >>> | Collaborative Online Management And Syndication Tools >>> | - - - - - - - - - - - - - - - - - - - - >>> >>> >>> >>> >>> >>> >>> ------------------------------------------------------- >>> Using Tomcat but need to do more? Need to support web services, >>> security? >>> Get stuff done quickly with pre-integrated technology to make your >>> job easier >>> Download IBM WebSphere Application Server v.1.0.1 based on Apache >>> Geronimo >>> http://sel.as-us.falkag.net/sel? >>> cmd=lnk&kid=120709&bid=263057&dat=121642 >>> _______________________________________________ >>> Sqlalchemy-users mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users >> >> >> >> >> ------------------------------------------------------- >> Using Tomcat but need to do more? Need to support web services, >> security? >> Get stuff done quickly with pre-integrated technology to make your >> job >> easier >> Download IBM WebSphere Application Server v.1.0.1 based on Apache >> Geronimo >> http://sel.as-us.falkag.net/sel? >> cmd=lnk&kid=120709&bid=263057&dat=121642 > > > All the advantages of Linux Managed Hosting--Without the Cost and > Risk! > Fully trained technicians. The highest number of Red Hat > certifications in > the hosting industry. Fanatical Support. Click to learn more > http://sel.as-us.falkag.net/sel? > cmd=lnk&kid=107521&bid=248729&dat=121642 > _______________________________________________ > Sqlalchemy-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users All the advantages of Linux Managed Hosting--Without the Cost and Risk! Fully trained technicians. The highest number of Red Hat certifications in the hosting industry. Fanatical Support. Click to learn more http://sel.as-us.falkag.net/sel?cmd=lnk&kid=107521&bid=248729&dat=121642 _______________________________________________ Sqlalchemy-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users
