Re: Error handling in plperl and pltcl

On Wednesday 01 December 2004 04:12, Thomas Hallgren wrote:
> Richard Huxton wrote:
> > Can I make some counter-proposals?
> >
> > 1. Wrap each function body/call (same thing here afaict) in a
> > sub-transaction. An exception can be caught within that function, and
> > all the spi in that function is then rolled back. This is rubbish, but
> > at least it's predictable and allows you to write to a log table and
> > throw another exception.
>
> This will be even worse since it will impose the subtransaction overhead
> on everything, even functions that never do any database access. Perhaps
> this approach would be feasible if imposed on volatile functions only,
> but then again, the volatility of a function cannot be trusted since we
> have no way of defining a "stable but with side effects" type.
>

Agreed.

> > 2. For pl/tcl introduce a pgtry { } catch { } which just starts a
> > sub-transaction and does standard try/catch. I don't use TCL, but from
> > the little I know this should be straightforward.
>
> If you know how to use special constructs like this, what's wrong with
> actually using savepoints verbatim? I.e.
>
> INSERT 1
> INSERT 2
> SAVEPOINT foo
> try {
> INSERT 3
> INSERT 4
> RELEASE foo
> }
> catch WHATEVER {
> ROLLBACK TO foo
> INSERT 5
> INSERT 6
> }
>
> IMHO a very clean, sensible, and easily understood approach that doesn't
> clobber the language.
>

Agreed. The fewer special constructs the better imho.

--
Robert Treat
Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL