Oracle 11g 的PL/SQL函数结果缓存

    模仿Oracle性能诊断艺术中的例子做了两个试验，书上说如果不用RELIES_ON，则函数依赖的对象发生的变更操作就不会导致结果缓存的失效操作(result_cache RELIES_ON(test1,test2))，试验证明不对，函数f1()并没有使用RELIES_ON，但表上的变化影响到了函数。

C:\Documents and Settings\guogang>sqlplus gg_test/[email protected]_gg

SQL*Plus: Release 10.2.0.1.0 - Production on 星期一 8月 4 19:46:44 2014
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
连接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE    11.2.0.1.0      Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> drop table test1 purge;
SQL> drop table test2 purge;
SQL> create table test1 as select * from dba_objects;
SQL> create table test2 as select * from all_objects;
SQL> select count(*) from test1;
  COUNT(*)
----------
     74144
SQL> select count(*) from test2;
  COUNT(*)
----------
     73248


SQL> create or replace function f1
   return number
   is
     l_ret number;
   begin
     select count(*) into l_ret
      from test1,test2
    where test1.object_type = test2.object_type
    and test1.object_type in ('TABLE SUBPARTITION','VIEW','INDEX','TABLE');
     return l_ret;
   end;
   /
函数已创建。


SQL> set timing on
SQL> select f1() from dual;
      F1()
----------
  60681409

已用时间:  00: 00: 07.29

--禁用结果缓存

SQL> execute dbms_result_cache.Bypass(bypass_mode=>true,session=>true);
SQL> select f1() from dual;
      F1()
----------
  60681409

已用时间:  00: 00: 03.60

--启用结果缓存

SQL> execute dbms_result_cache.Bypass(bypass_mode=>false,session=>true);
SQL> select f1() from dual;
      F1()
----------
  60681409
已用时间:  00: 00: 00.00


SQL> delete from test1 where object_type = 'VIEW' and rownum <100;
SQL> delete from test2 where object_type = 'VIEW' and rownum <100;
SQL> commit;
SQL> select f1() from dual;
      F1()
----------
  59788330

已用时间:  00: 00: 07.09  --可以看到数据发生变化，即使不使用RELIES_ON，结果集也是正确的。

SQL> select count(*)
      from test1, test2
     where test1.object_type = test2.object_type
     and test1.object_type in ('TABLE SUBPARTITION','VIEW','INDEX','TABLE');
  COUNT(*)
----------
  59788330
已用时间:  00: 00: 03.56   


SQL> create or replace function f2
   return number
     result_cache RELIES_ON(test1,test2)
   is
     l_ret number;
   begin
     select count(*) into l_ret
      from test1,test2
    where test1.object_type = test2.object_type
    and test1.object_type in ('TABLE SUBPARTITION','VIEW','INDEX','TABLE');
     return l_ret;
   end;
   /
函数已创建。


SQL> select f2() from dual;
      F2()
----------
  59788330
已用时间:  00: 00: 03.54
SQL> select f2() from dual;
      F2()
----------
  59788330
已用时间:  00: 00: 00.00

SQL> delete from test1 where object_type = 'VIEW' and rownum <100;
SQL> delete from test2 where object_type = 'VIEW' and rownum <100;
SQL> commit;
SQL> select f2() from dual;
      F2()
----------
  58914853

已用时间:  00: 00: 03.50

SQL> select count(*)
      from test1, test2
     where test1.object_type = test2.object_type
     and test1.object_type in ('TABLE SUBPARTITION','VIEW','INDEX','TABLE');
  COUNT(*)
----------
  58914853
已用时间:  00: 00: 03.50