Thanks for responding. Here's a simple example of the kind of thing I'm trying to do:

postgres=# drop type complex;
DROP TYPE
postgres=# create type complex as (r numeric, i numeric);
CREATE TYPE
postgres=# create domain unitary as complex;
ERROR: "complex" is not a valid base type for a domain
postgres=#

The idea in this example would be to create a domain of complex numbers where
r*r + i*i is not zero.

Are composite types not useable for domains?

----- Original Message ----
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Winkler <the_andrew_winkler@yahoo.com>
Cc: pgsql-novice@postgresql.org
Sent: Tuesday, January 15, 2008 8:55:34 PM
Subject: Re: [NOVICE] domains, types, constraints


Andrew Winkler <the_andrew_winkler@yahoo.com> writes:
> I'm having trouble with types and domains. I can create a type, but
then when I try to create constraints
> using the components of the type, I get syntax errors. I've read
through the pdf several times, to no avail.
> Things like (value).component, component(value), value::component,
for example, all generate errors.

This is nearly content-free :-(. Show us exactly what commands you
tried and what errors you got. (Cut and paste from a terminal window
is good.)

regards, tom lane

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Andrew Winkler <the_andrew_winkler@yahoo.com> writes:
> postgres=# create type complex as (r numeric, i numeric);
> CREATE TYPE
> postgres=# create domain unitary as complex;
> ERROR: "complex" is not a valid base type for a domain

> Are composite types not useable for domains?

Nope, sorry. We currently only support domains over base types.

I don't think anyone's even thought about doing the above, though
it does seem like a potentially useful thing.

regards, tom lane

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