Need help with select stmnt but not loosing unique index scan...

Question

it's 10 g
any way to get this faster using uniqe index?
select * from my_test3
where c1 = :a_value
and c3 = maximum value by c1....
Any work arround so that i do not loose my unique index scan..
i know I can use subquery or some..but that is not a good solution...
SQL> drop table my_test3;
Table dropped.
SQL>
SQL> create table my_test3
  2  (c1 number ,
  3   c3 timestamp );
Table created.
SQL> alter table my_test3
  2   add primary key(c1,c3);
Table altered.
SQL>
SQL> insert into my_test3  values(1,systimestamp);
1 row created.
SQL> insert into my_test3  values(1,systimestamp);
1 row created.
SQL> insert into my_test3  values(1,systimestamp);
1 row created.
SQL> insert into my_test3  values(1,systimestamp);
1 row created.
SQL> insert into my_test3  values(2,systimestamp);
1 row created.
SQL> insert into my_test3  values(3,systimestamp);
1 row created.
SQL> insert into my_test3  values(3,systimestamp);
1 row created.
SQL> insert into my_test3  values(5,systimestamp);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> set line 130
SQL> set long 400000
SQL> explain plan for
  2  select * from my_test3
  3  where c1 = :val2
  4  and c3 = :val4;
Explained.
SQL> SELECT * FROM TABLE(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 964817202
| Id  | Operation         | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |              |     1 |    26 |     1   (0)| 00:00:01 |
|*  1 |  INDEX UNIQUE SCAN| SYS_C0047363 |     1 |    26 |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
   1 - access("C1"=TO_NUMBER(:VAL2) AND "C3"=TO_TIMESTAMP(:VAL4))
13 rows selected.
SQL>

Answer 1

select my.c2 as c1, my.c3 as c3 from (select t3.c1 c2, t3.c3, max(t3.c3) over (partition by t3.c1 ) as cme from my_test3 t3) my
where my.c3 = cme
C1 C3
1 07-MAY-08 01.26.26.617994 PM
2 07-MAY-08 01.26.26.621817 PM
3 07-MAY-08 01.26.26.628041 PM
5 07-MAY-08 01.26.26.631821 PM
| Id  | Operation         | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |              |     8 |   312 |     2   (0)| 00:00:01 |
|*  1 |  VIEW             |              |     8 |   312 |     2   (0)| 00:00:01 |
|   2 |   WINDOW BUFFER   |              |     8 |   208 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN| SYS_C0025048 |     8 |   208 |     2   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   1 - filter("MY"."C3"="CME")
Note
   - dynamic sampling used for this statementYou'll need to see if you lose the index or not...