Oracle 11g结果集缓存限制

Oracle 11g结果集缓存限制

有个不大的表 数据量大于百万级别 这是类似IP地址范围查找. 表的查询量很大.数实时生成,有时会被更新该表上的索引 主键和表 都被我KEEP进内存了。
查询速度 基本保持在50-30毫秒之间.
该表的数据 一天要查500万次以上.同时被重复查询的次数也蛮多子.

鉴于这个原因 所以向开发人员提出 在SQL 增加提示 /*+ result_cache */

结论是 结果缓存通过表的依赖而失效,也就是说相应表发生了数据变化那么就重新从表获取.相比时间 比普通45毫秒 高很多 达到945毫秒. 难道它不晓得从内存中获取吗? 还是觉得表数据有变化,直接从硬盘上读取才是真!

declare

B1 VARCHAR2(20);

B2 NUMBER;

ORG NUMBER(10);

S  TIMESTAMP;

E  TIMESTAMP;

R  TIMESTAMP;

begin

  B2:=12;

  B1:=668239581895;

FOR I IN 1..100 LOOP

 

S:=SYSTIMESTAMP;

SELECT  /*+ result_cache */ USE_IP into  IP

  FROM (SELECT A.USE_IP

              A.IP_TYPE

          FROM BACK_IP A

        WHEREA.IP_TYPE IN (3, 5, 9)

          ANDIP_LEGN = B2

          ANDA.START_IP <= B1

          ANDA.END_IP >= B1

        ORDER BYA.DISP_DATE DESC,

                  A.CREATE_TIME  DESC)

WHERE ROWNUM <= 1;

E:=SYSTIMESTAMP;

DBMS_OUTPUT.PUT_LINE(TO_CHAR(E-S));

DBMS_LOCK.SLEEP(10);

END LOOP;

END ;

测试结果 不很理想 波动性太大了.

+00000000000:00:00.090374000

+00000000000:00:00.102860000

+00000000000:00:00.000237000

+00000000000:00:00.000139000

+00000000000:00:00.000135000

+00000000000:00:00.000163000

+00000000000:00:00.000170000

+00000000000:00:00.000206000

+00000000000:00:00.000173000

+000000000 00:00:00.000171000

+00000000000:00:00.000170000

+00000000000:00:00.000139000

+00000000000:00:00.000267000

+00000000000:00:00.000171000

+00000000000:00:00.000160000

+00000000000:00:00.000180000

+00000000000:00:00.000161000

+00000000000:00:00.000183000

+00000000000:00:00.000182000

+00000000000:00:00.000139000

+00000000000:00:00.000147000

+00000000000:00:00.000160000

+00000000000:00:00.000212000

+00000000000:00:00.000353000

+00000000000:00:00.094454000