2012/1/4 Koen Deforche <k...@emweb.be>
> Hey Dmitriy,
>
> 2012/1/4 Dmitriy Igrishin <dmit...@gmail.com>:
> > Well, suppose that the Transaction::~Transaction() looks like:
> > Transaction::~Transaction()
> > {
> > if (std::uncaught_exception()) {
> > // tries to rollback
> > } else {
> > // tries to commit
> > }
> > }
> >
> > And suppose My_class::~My_class() looks like:
> > My_class::~My_class()
> > {
> > try {
> > Transaction t(........);
> > // some actions ...
> > } catch (...) {
> > // some actions ...
> > }
> > }
> >
> > Then,
> > void f(......)
> > {
> > My_class obj(.....);
> > throw 1;
> > }
> > Opps and ugh, because the transaction in the
> > My_class::~My_class() will be rolled back because
> > of stack unwinding instead of commit!
>
> Okay, that's a case we hadn't thought of.
>
> But is it realistic to start transactions in a destructor of a
> stack-based object?
>
Yes, it is. At least in PostgreSQL, each command
that is performed out of the explicitly opened transaction
block runs in the separate transaction. There are
a lot of commands which are intended to free resources
on the server side, such as cursors (CLOSE command),
savepoints (RELEASE SAVEPOINT command),
listeners (UNLISTEN command), the DISCARD command,
or even the applications specific (advisory) locks.
>
> In either case, you can still add a t.commit(). In fact, I believe
> that people will see more transactions rollback (I know I have)
> because they forgot to commit() the transaction in each code path,
> than this particular case (in which case you can still add the
> explicit commit()).
>
Yes, but personally I think that this makes the API more
complex and error-prone, since the user must know about
a gotcha which I mentioned above.
Anyway, it is just my point of view, if you don't see the
problem here and you sure that the users need this feature,
I don't mind.
--
// Dmitriy.
------------------------------------------------------------------------------
Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex
infrastructure or vast IT resources to deliver seamless, secure access to
virtual desktops. With this all-in-one solution, easily deploy virtual
desktops for less than the cost of PCs and save 60% on VDI infrastructure
costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
_______________________________________________
witty-interest mailing list
witty-interest@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/witty-interest
