On Tue, Jul 9, 2013 at 5:35 PM, Frank Millman <fr...@chagford.com> wrote: > I have been following this sub-thread with interest, as it resonates with > what I am doing in my project.
Just FYI, none of my own code will help you as it's all using libpqxx, but the docs for the library itself are around if you want them (it's one of the standard ways for C++ programs to use PostgreSQL). > I came up with the following context manager - > > class DbSession: > def __exit__(self, type, exc, tb): > if self.transaction_active: > self.conn.commit() > self.transaction_active = False Hmm. So you automatically commit. I'd actually be inclined to _not_ do this; make it really explicit in your code that you now will commit this transaction (which might throw an exception if you have open subtransactions). The way the code with libpqxx works is that any transaction (including a subtransaction) must be explicitly committed, or it will be rolled back. So there's one possible code path that results in persistent changes to the database, and anything else won't: * If the object expires without being committed, it's rolled back. * If an exception is thrown and unwinds the stack, roll back. * If a Unix signal is sent that terminates the program, roll back. * If the process gets killed -9, definitely roll back. * If the computer the program's running on spontaneously combusts, roll back. * If the hard drive is physically ripped from the server during processing, roll back. (Note though that most of these guarantees are from PostgreSQL, not from libpqxx. I'm talking about the whole ecosystem here, not something one single library can handle.) I have absolute 100% confidence that nothing can possibly affect the database unless I explicitly commit it (aside from a few non-transaction actions like advancing a sequence pointer, which specifically don't matter (rolled back transactions can result in gaps in a sequence of record IDs, nothing more)). It's an extremely comfortable work environment - I can write whatever code I like, and if I'm not sure if it'll work or not, I just comment out the commit line and run. *Nothing* can get past that and quietly commit it behind my back. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
