On Mon, 2011-01-03 at 19:01 +0200, Heikki Linnakangas wrote:
> > If we do that, then we definitely need a catch-all WHEN statement, so
> > that we can say
> >
> > WHEN NOT MATCHED
> > INSERT
> > WHEN MATCHED
> > UPDATE
> > ELSE
> > { INSERT into another table so we can try again in a minute
> > or RAISE error }
> >
> > Otherwise we will silently drop rows. Throwing an error every time isn't
> > useful behaviour.
>
> An ELSE clause would be nice, but it's not related to the question at
> hand. Only some serialization anomalities result in a row that matches
> neither WHEN MATCHED nor WHEN NOT MATCHED.
Concurrent UPDATEs, DELETEs, MERGE
> Others result in a duplicate
> key exception, for example.
Concurrent INSERTs, MERGE
So an ELSE clause is very relevant to handling anomalies in a useful
way.
-- Simon Riggs http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services