Re: BUG #2375: ALTER COLUMN TYPE on composite types - Mailing list pgsql-bugs

"George Barbarosie" <george.barbarosie@gmail.com> writes:
> CREATE TYPE composite AS (
>     label varchar(20),
>     data  varchar(1000) );

> CREATE TYPE composite2 AS (
>     label   varchar(20),
>     data    text );

> CREATE CAST (composite as composite2) WITHOUT FUNCTION AS IMPLICIT;

The above is invalid --- since values of composite types have their type
OID embedded in them, a coercion can't simply be a relabeling.  You've
used your superuser powers to break the system, as is all too easy with
binary casts :-(

            regards, tom lane