create type dimensions as (
  width integer,
  height integer,
  depth integer
);

create table moving_boxes (
  id serial primary key,
  dims dimensions not null
);

insert into moving_boxes (dims) values (row(3,4,5)::dimensions);

> select pg_database_size('hr_hotels');
 pg_database_size
------------------
          8249516

> select pg_relation_size('reservations');
 pg_relation_size
------------------
          1531904

> select pg_size_pretty(pg_relation_size('users_pkey'));
 pg_size_pretty
----------------
 240 kB