Re: WIP: Range Types

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Excerpts from Robert Haas's message of mié ene 12 13:48:27 -0300 2011:
>> I guess that begs the question of why we need to allow users to call
>> type output functions directly.

> It used to be the case that that was the only way to run certain casts.
> For example, see the pre-8.2 version of this:
> http://wiki.postgresql.org/wiki/Pg_depend_display

> I haven't needed to use that in a long time, but I am not sure if the
> need has completely disappeared.

The general point is that any out-of-band data transmitted to an output
function has to be trustworthy, and it has to be available at any place
that is going to call the output function.  The latter point tends to
put a crimp in any ideas of this sort anyway: if you can derive the info
you want at any arbitrary place in the system, why not derive it inside
the output function to start with?
        regards, tom lane