DECLARE
  q varchar2(4000);
begin 


здесь надо пробежать по таблице и перед построением дерева собрать long_number

  q:='   select case when connect_by_isleaf = 1 then 0 ';
  q:=q||'       when level = 1             then 1 ';
  q:=q||'       else                           -1 ';
  q:=q||'       end as status,  ';  
  q:=q||'  level, ';
  q:=q||'       long_number || '' '' || unit_name	 as title,';
  q:=q||'    ''icon-gear'' as  icon, ';
 q:=q||'   ID_REESTR as value, ';
 q:=q||'   null as tooltip, ';
 q:=q||'  ''javascript:pageItemValue(''||apex_escape.js_literal(ID_REESTR)||''); pageItemValue2(''||apex_escape.js_literal(unit_name)||'');'' as link ';
 q:=q||'   from REESTR';
 q:=q||'   connect by prior ID_REESTR = ID_PARENT  ';

 
 
  if :f_vid != 'ALL'   then
    q:=q||'start with vid= :f_vid ';

  else
  q:=q||'  start with ID_REESTR=1  ';
  end if;

  return q;
end;

long_number || '' '' || unit_name	 as title,';

select case when connect_by_isleaf = 1 then 0
            when level = 1             then 1
            else                           -1
       end as status, 
       level, 
       
       ltrim(sys_connect_by_path(rn, '.'), '.') || ' ' || unit_name	 as title, 
       'icon-gear' as icon, 
       ID_REESTR as value, 
       null as tooltip, 
       null as link 
      
       
from (select reestr.*, row_number() over (partition by id_parent order by short_number) rn  
   from reestr 
  )  
start with ID_REESTR=1
connect by prior ID_REESTR = ID_PARENT 

UPDATE reestr
SET long_number= (
select ltrim(sys_connect_by_path(case when level > 2 then rn end, '.'), '.') 
FROM
  (select reestr.*, row_number() over (partition by id_parent order by short_number) rn
   from reestr)   
start with id_reestr =1
connect by prior id_reestr = id_parent) AA
WHERE reestr.id_reestr= AA.id_reestr ;

MERGE into reestr t1
      using (select id_reestr, ltrim(sys_connect_by_path(case when level > 2 then rn end, '.'), '.') pth
FROM
  (select reestr.*, row_number() over (partition by id_parent order by short_number) rn
   from reestr)   
start with id_reestr =1
connect by prior id_reestr = id_parent) t2
      on (t1.id_reestr = t2.id_reestr )
      when matched then 
        update 
         set t1.long_number = t2.pth;