create cluster username_cluster# ( username varchar2(30) ) 
hashkeys 100 size 50;

create table user_cluster
cluster username_cluster# ( username )
as
select * from all_users;

create table user_regular as select * from all_users;

create unique index user_regular_idx on user_regular(username);

alter table user_regular modify user_id null;
alter table user_cluster modify user_id null;

alter session set sql_trace = true;

declare
  l_user_id user_regular.user_id%type;
begin
  for c in (select owner from objs_regular where owner <> 'PUBLIC')
  loop
    select user_id into l_user_id from user_regular where username = c.owner;
    select user_id into l_user_id from user_cluster where username = c.owner;
  end loop;
end;
/

alter session set sql_trace = false;


