--
-- tree_increment_key/1
--
create or replace function tree_increment_key(
  bit varying
) returns varbit as $$

declare
    p_child_sort_key                alias for $1;
    v_child_sort_key                integer;
begin
    if p_child_sort_key is null then
        v_child_sort_key := 0;
    else
        v_child_sort_key := tree_leaf_key_to_int(p_child_sort_key) + 1;
    end if;

    return int_to_tree_key(v_child_sort_key);
end;$$ language plpgsql;