Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("B"."NAME"='sss')
4 - access("A"."RN"="B"."RN")
18 rows selected.
非in-list和嵌套循环操作，调整这个参数时，不会影响oracle优化器成本的运算，如下
SQL> set linesize 200 pagesize 999
SQL> explain plan for select * from t where rn<200;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 470836197
-------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 199 | 4179 | 3 (0)| 00:00:35 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 199 | 4179 | 3 (0)| 00:00:35 |
|* 2 | INDEX RANGE SCAN | T_IDX | 199 | | 2 (0)| 00:00:24 |
-------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("RN"<200)
14 rows selected.
SQL> alter session set optimizer_index_caching=1;
Session altered.
SQL> explain plan for select * from t where rn<200;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 470836197
-------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 199 | 4179 | 3 (0)| 00:00:35 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 199 | 4179 | 3 (0)| 00:00:35 |
|* 2 | INDEX RANGE SCAN | T_IDX | 199 | | 2 (0)| 00:00:24 | --可以看到cost确实没有改变
-------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("RN"<200)
14 rows selected.