[Ur] Exceptions handling

[Vladimir Shabanov]

2010/9/5 Adam Chlipala <adamc at impredicative.com>:
> I've started implementing this.  Everything works, save that the semantics
> differs between Postgres and MySQL/SQLite.  Postgres won't let you continue
> using a transaction after one command has failed, whereas MySQL and SQLite
> allow many errors within one transaction.  (Remember that every Ur/Web page
> execution is implicitly inside a single transaction.)  What does everyone
> think about whether that semantics is acceptable for Ur/Web?  The more
> liberal semantics can be implemented for Postgres using savepoints, but it
> would decrease performance.  If no one would want to keep running SQL after
> an error, then there doesn't seem to be a reason to do more work.
>
> Personally, I'm in favor of never using this new feature, anyway, but I'm
> interested in what y'all who argued for it think. :)

I think it would be nice to have possibility to manually restart
transaction so DB still can be accessed after error.