"Daniel Schuchardt" <daniel_schuchardt(at)web(dot)de> writes:
> Why this? With PostrgreSql 7.2 this works well.
7.3 tries to enforce type safety (with 7.2 it's trivial to create type
definitions that crash the server when used). Your type declaration
doesn't pass because the I/O functions are declared to be for int4,
not lo.
My advice as of 7.3 would be to create type lo as a domain alias for
type OID:
regression=# create domain lo as oid;
CREATE DOMAIN
regards, tom lane