sql当hints index fast full scan走不了 会走index range scan的情况

explain plan for 
select  /*+INDEX_FFS(a t100_idx1)*/ owner  from t100 a where a.owner='TLCBUSER';

select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT
Plan hash value: 4259608525
 
----------------------------------------------------------------------------------
| Id  | Operation            | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |           |  3962 | 27734 |    67   (2)| 00:00:01 |
|*  1 |  INDEX FAST FULL SCAN| T100_IDX1 |  3962 | 27734 |    67   (2)| 00:00:01 |
----------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - filter("A"."OWNER"='TLCBUSER')
   
 explain plan for 
select  /*+INDEX_FFS(a t100_idx1)*/ owner ,a.object_name from t100 a where a.owner='TLCBUSER';

select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT
Plan hash value: 1209239783
 
-----------------------------------------------------------------------------------------
| Id  | Operation                   | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |           |  3962 |   123K|   111   (0)| 00:00:02 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T100      |  3962 |   123K|   111   (0)| 00:00:02 |
|*  2 |   INDEX RANGE SCAN          | T100_IDX1 |  3962 |       |    10   (0)| 00:00:01 |
-----------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   2 - access("A"."OWNER"='TLCBUSER')