SQL> set autotrace trace explain statistics
SQL> select client_id,service_date,other_stuff
  2    from client_usage
  3    where (client_id,service_date) in(
  4      select client_id,min(service_date)
  5         from client_usage
  6         group by client_id
  7       union all select client_id,max(service_date)
  8         from client_usage
  9         group by client_id
 10    );

Elapsed: 00:00:01.14

Execution Plan
----------------------------------------------------------
Plan hash value: 133001550

------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                 |     2 |    90 |  1180   (1)| 18:25:41 |
|   1 |  NESTED LOOPS                |                 |       |       |            |          |
|   2 |   NESTED LOOPS               |                 |     2 |    90 |  1180   (1)| 18:25:41 |
|   3 |    VIEW                      | VW_NSO_1        |     2 |    44 |  1176   (1)| 18:21:56 |
|   4 |     HASH UNIQUE              |                 |     2 |    22 |  1176  (51)| 18:21:56 |
|   5 |      UNION-ALL               |                 |       |       |            |          |
|   6 |       HASH GROUP BY          |                 |     1 |    11 |   588   (1)| 09:10:58 |
|   7 |        INDEX FAST FULL SCAN  | PK_CLIENT_USAGE |   788K|  8472K|   587   (0)| 09:10:02 |
|   8 |       HASH GROUP BY          |                 |     1 |    11 |   588   (1)| 09:10:58 |
|   9 |        INDEX FAST FULL SCAN  | PK_CLIENT_USAGE |   788K|  8472K|   587   (0)| 09:10:02 |
|* 10 |    INDEX UNIQUE SCAN         | PK_CLIENT_USAGE |     1 |       |     1   (0)| 00:00:57 |
|  11 |   TABLE ACCESS BY INDEX ROWID| CLIENT_USAGE    |     1 |    23 |     2   (0)| 00:01:53 |
------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

  10 - access("CLIENT_ID"="CLIENT_ID" AND "SERVICE_DATE"="MIN(SERVICE_DATE)")


Statistics
----------------------------------------------------------
          0  recursive calls
          1  db block gets
       6210  consistent gets
          0  physical reads
         52  redo size
        768  bytes sent via SQL*Net to client
        519  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          2  rows processed

SQL>
SQL> set autotrace trace explain statistics
SQL> select client_id
  2        ,service_date
  3        ,other_stuff
  4    from (
  5          select client_id
  6                ,service_date
  7                ,other_stuff
  8                ,row_number() over (partition by client_id order by service_date) rn_min
  9                ,row_number() over (partition by client_id order by service_date desc) rn_max
 10            from client_usage
 11         )
 12   where (rn_min = 1 OR rn_max = 1) ;

Elapsed: 00:00:07.52

Execution Plan
----------------------------------------------------------
Plan hash value: 690079770

---------------------------------------------------------------------------------------------
| Id  | Operation            | Name         | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |              |   788K|    48M|       | 11313   (1)|176:40:17 |
|*  1 |  VIEW                |              |   788K|    48M|       | 11313   (1)|176:40:17 |
|   2 |   WINDOW SORT        |              |   788K|    17M|    27M| 11313   (1)|176:40:17 |
|   3 |    WINDOW SORT       |              |   788K|    17M|    27M| 11313   (1)|176:40:17 |
|   4 |     TABLE ACCESS FULL| CLIENT_USAGE |   788K|    17M|       |   589   (0)| 09:11:54 |
---------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN_MIN"=1 OR "RN_MAX"=1)


Statistics
----------------------------------------------------------
         27  recursive calls
         23  db block gets
       3092  consistent gets
       7156  physical reads
         52  redo size
        768  bytes sent via SQL*Net to client
        519  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          2  sorts (disk)
          2  rows processed