模拟Oracle性能诊断艺术做了两个试验样品。书上说的不承担RELIES_ON。果缓存的失效操作(result_cache RELIES_ON(test1,test2))。试验证明不正确，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/gg_test@10.10.15.25_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 --能够看到数据发生变化，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
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