--
-- rel_segment__get/2
--
create or replace function rel_segment__get(
  integer,
  character varying
) returns int4 as $$

declare
  get__group_id         alias for $1;  
  get__rel_type         alias for $2;  
begin

   return min(segment_id)
   from rel_segments
   where group_id = get__group_id
     and rel_type = get__rel_type;
  
end;$$ language plpgsql;