declare
        v_parent_sk     varbit default null;
        v_max_value     integer;
        v_rec           record;
        clr_keys_p      boolean default 't';
begin
        if new.folder_id = old.folder_id and 
           ((new.parent_id = old.parent_id) or 
            (new.parent_id is null and old.parent_id is null)) then

           return new;

        end if;

        for v_rec in select folder_id, parent_id
                       from sp_folders 
                      where tree_sortkey between new.tree_sortkey and tree_right(new.tree_sortkey)
                   order by tree_sortkey
        LOOP
            if clr_keys_p then
               update sp_folders set tree_sortkey = null
               where tree_sortkey between new.tree_sortkey and tree_right(new.tree_sortkey);
               clr_keys_p := 'f';
            end if;
            
            select max(tree_leaf_key_to_int(tree_sortkey)) into v_max_value
              from sp_folders 
              where parent_id = v_rec.parent_id;

            select tree_sortkey into v_parent_sk 
              from sp_folders 
             where folder_id = v_rec.parent_id

            update sp_folders 
               set tree_sortkey = tree_next_key(v_parent_sk, v_max_value)
             where folder_id = v_rec.folder_id;

        end LOOP;

        return new;

end;