tfo@monsterlabs.com writes:
> is it a known issue that \df in psql does not list functions that return
> opaque (i.e., those used in triggers)?
I believe this was done deliberately as a means of suppressing I/O
conversion functions from the display. I'm not sure I agree with that,
and I am sure that it hides more stuff than just conversion functions,
but that was the rationale.
There's been talk on pghackers of breaking down the notion of type
"opaque", which is presently overloaded to mean about half a dozen
different things, into several pseudo-types that would have crisper
definitions. That would probably make it possible to identify I/O
functions with much more reliability, and so improve the accuracy
of \df's filtering of "uninteresting" functions.
regards, tom lane