Re: Can I trigger an action from a coalesce ?

On Sat, Feb 22, 2020 at 01:06:57PM -0800, Christophe Pettus wrote:
>
>
> > On Feb 22, 2020, at 13:05, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> wrote:
> >
> > On 2/22/20 1:02 PM, stan wrote:
> >> I have a case where if a value does not exist, I am going to use a default,
> >> which is easy with coalesce. But I would like to warn the user that a
> >> default has been supplied. The default value is reasonable, and could
> >> actually come from the source table, so I can't just check the value.
> >> I'd like to do a raise NOTICE, if the default portion of the coalesce fires.
> >> Anyone have a good way to accomplish this?
> >
> > No.
>
> You can, of course, create a PL/pgSQL function and use that as the default.
I suppose you are suggesting that the function try the original SELECT, and
if it returns a NULL then retun the default AND do the raise NOTICE?

Or is there a simpler way?

--
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
-- Benjamin Franklin