Oracle SQL Plan operation PARTITION LIST (INLIST)

create table tq84_tab_part (
   id     number(5),
   val    number(5,1),
   grp    char(1)  not null check (grp in ('A', 'B', 'C')),
   --
   constraint tq84_tab_part_pk primary key (id)
)
partition by list (grp) (
   partition tq84_list_partition_A values ('A'),
   partition tq84_list_partition_B values ('B'),
   partition tq84_list_partition_C values ('C')
);

begin
   dbms_random.seed(42);
end;
/

insert into tq84_tab_part
select
   level,
   round(dbms_random.value(0, 1000), 1),
   chr(ascii('A') + dbms_random.value(0, 3))
from
   dual connect by level <= 10000;


explain plan for
   select
      grp,
      max(val) max_val
   from
      tq84_tab_part
   where
      grp in ('A', 'B')
   group by
      grp;
;

--
-- -----------------------------------------------
-- | Id  | Operation             | Name          |
-- -----------------------------------------------
-- |   0 | SELECT STATEMENT      |               |
-- |   1 |  PARTITION LIST INLIST|               |
-- |   2 |   HASH GROUP BY       |               |
-- |   3 |    TABLE ACCESS FULL  | TQ84_TAB_PART |
-- -----------------------------------------------

select * from table(dbms_xplan.display(format=>'basic'));

drop   table tq84_tab_part;