Yvon Thoraval <yvon(dot)thoraval(at)gmail(dot)com> writes:
> CREATE FUNCTION has_infos(text) RETURNS boolean AS 'select
> character_length($1) > 0;' LANGUAGE SQL IMMUTABLE RETURNS FALSE ON NULL
> INPUT;
FWIW, "RETURNS NULL ON NULL INPUT" is a formulaic phrase specified
in the SQL standard. It's not meant to be something you can plug an
arbitrary value into --- it has to be written exactly that way.
The traditional Postgres term is just "STRICT", which means precisely
the same thing.
regards, tom lane