Oracle hint: USE_CONCAT

create table tq84_xy (
   id   integer primary key,
   val  number  ( 7,2) not null,
   x    varchar2(10  ) not null,
   y    varchar2(10  ) not null
);

create index tq84_ix_x on tq84_xy(x);
create index tq84_ix_y on tq84_xy(y);

begin
   dbms_random.seed(2808);

   insert into tq84_xy
   select
      level,
      dbms_random.value(100, 100000),
      dbms_random.string('a', 10),
      dbms_random.string('a', 10)
   from
      dual connect by level <= 10000;

   dbms_stats.gather_table_stats(user, 'tq84_xy');
end;
/

explain plan for
select
   val
from
   tq84_xy
where
   x = 'hMZLVdpoub' or
   y = 'xFOwpLURXi';

select * from dbms_xplan.display(format=>'basic');
--
-- ---------------------------------------------------------
-- | Id  | Operation                           | Name      |
-- ---------------------------------------------------------
-- |   0 | SELECT STATEMENT                    |           |
-- |   1 |  TABLE ACCESS BY INDEX ROWID BATCHED| TQ84_XY   |
-- |   2 |   BITMAP CONVERSION TO ROWIDS       |           |
-- |   3 |    BITMAP OR                        |           |
-- |   4 |     BITMAP CONVERSION FROM ROWIDS   |           |
-- |   5 |      INDEX RANGE SCAN               | TQ84_IX_X |
-- |   6 |     BITMAP CONVERSION FROM ROWIDS   |           |
-- |   7 |      INDEX RANGE SCAN               | TQ84_IX_Y |
-- ---------------------------------------------------------

explain plan for
select /*+ use_concat */
   val
from
   tq84_xy
where
   x = 'hMZLVdpoub' or
   y = 'xFOwpLURXi';

select * from dbms_xplan.display(format=>'basic');
--
-- ----------------------------------------------------------
-- | Id  | Operation                            | Name      |
-- ----------------------------------------------------------
-- |   0 | SELECT STATEMENT                     |           |
-- |   1 |  CONCATENATION                       |           |
-- |   2 |   TABLE ACCESS BY INDEX ROWID BATCHED| TQ84_XY   |
-- |   3 |    INDEX RANGE SCAN                  | TQ84_IX_Y |
-- |   4 |   TABLE ACCESS BY INDEX ROWID BATCHED| TQ84_XY   |
-- |   5 |    INDEX RANGE SCAN                  | TQ84_IX_X |
-- ----------------------------------------------------------

drop table tq84_xy;