> If you want ORDER BY on the column to default to your custom ordering,
> the only way is a distinct datatype that you can make your custom
> opclass be the default for.
>
> The domain idea might work, I'm not totally sure. Defining
> functions/operators on a domain is a bit ticklish because anything but
> an exact match will get smashed to the domain base type and thus not
> match your function. I think though that in this case you might get
> away with it because it would be an exact match --- it's worth a try
> anyway.
I gave it a try but
a) my original problem appeared: I can not specify a limit for a domain type:
db=> create domain vchar as varchar; CREATE DOMAIN db=> create temp table a(a vchar(10)); ERROR: syntax error at
ornear "(" at character 28 LINE 1: create temp table a(a vchar(10));
b) the sort order is the same as for varchar with my custom opclass (creating with default for type vchar).
So I will end up with my own type (for in/out functions simply calling that ones from varchar)
and using "user defined typmod" if available in an upcoming release.
Would it be a nice feature for standard postgres to support such a type? ;-)
The compare function simply would be:
if(len_left < len_right) return -1;
else if(len_left > len_right) return 1;
else return strncmp(left, right, len_left);
Thank you for discussion,
Michael