Federico Di Gregorio wrote: > On 19/10/11 09:59, M.-A. Lemburg wrote: > [snip] >>> risks to become a problem, with the close() that may raise an error >>>> because the connection has been implicitly closed by a communication >>>> error. Note that close() in itself often is a quite safe operation, >>>> not involving database communication, so it is not expected to fail >>>> and may not be well guarded. >> That last sentence is not quite correct: .close() issues an implicit >> .rollback() and usually also tells the database backend to free up >> resources maintained for the connection, so it does require communication >> with the backend. > > Here is the problem. Does .close() always issue an implicit .rollback()?
Yes. > The DBAPI says yes but, as noted previously, the driver can choose to > NOT send a rollback. Not if it complies to the DB-API. > In fact on the second .close() the driver SHOULD > NOT send a rollback because there is no transaction in progress. The second .close() would in that case raise an exception as per the definition in the database, since it has become unusable :-) BTW: Regardless of whether the driver explicitly issues a rollback or not, the database backend will roll back the connection if the connection closes and there's a pending transaction. > I'd vote for idempotent .close() interpretation too. Please read my full reply: the implicit rollback is not the only operation that can fail. Silencing errors is not a good idea. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Oct 19 2011) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ ::: Try our new mxODBC.Connect Python Database Interface for free ! :::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 http://www.egenix.com/company/contact/ _______________________________________________ DB-SIG maillist - DB-SIG@python.org http://mail.python.org/mailman/listinfo/db-sig
