Oracle 11g PL/SQL function result cache, oracle11g
Two experiments have been conducted to simulate the Oracle Performance Diagnosis art. The book says that if you don't need RELIES_ON, then the changes to the objects on which the function depends will not result in the invalid result cache operation (result_cache RELIES_ON (test1, test2). The test proves that this operation is incorrect. The function f1 () does not use RELIES_ON, however, changes in the table affect the function.
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 Monday August 4 19:46:44 2014
Copyright (c) 1982,200 5, Oracle. All rights reserved.
Connect:
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
Rochelle 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;
/
The function has been created.
SQL> set timing on
SQL> select f1 () from dual;
F1 ()
----------
60681409
Used time: 00: 00: 07.29
-- Disable result caching
SQL> execute dbms_result_cache.Bypass (bypass_mode => true, session => true );
SQL> select f1 () from dual;
F1 ()
----------
60681409
Used time: 00: 00: 03.60
-- Enable result caching
SQL> execute dbms_result_cache.Bypass (bypass_mode => false, session => true );
SQL> select f1 () from dual;
F1 ()
----------
60681409
Used time: 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
Time used: 00: 00: 07.09 -- you can see that the data has changed. Even if you do not use RELIES_ON, The result set is correct.
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
Used time: 00: 00: 03.56
SQL> create or replace function f2
Return number
Result_cache RELIES_ON (test1, test2)
Is
Rochelle 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;
/
The function has been created.
SQL> select f2 () from dual;
F2 ()
----------
59788330
Used time: 00: 00: 03.54
SQL> select f2 () from dual;
F2 ()
----------
59788330
Used time: 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
Used time: 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
Used time: 00: 00: 03.50
Oracle 11g pl/SQL
If the updated results are pre-displayed, execute the following statement:
Select deptno, empno, sal, decode (deptno, 10, '5% ', 20, '000000', 30, '000000') "sal % ",
Decode (deptno, 10, sal * 1.05, 20, sal * 1.1, 30, sal * 1.15) newsal
From emp order by deptno, empno;
To update and display the data first, you must add the updated column newsal to the table structure. Otherwise, the pre-Update salary cannot be output.
Update emp x newset sal = (select decode (deptno, 10, sal * 1.05, 20, sal * 1.1, 30, sal * 1.15)
From emp where empno = x. empno );
Display: select deptno, empno, sal, decode (deptno, 10, '5% ', 20, '123', 30, '123') "sal %", newsal
From emp order by deptno, empno;
PL/SQL query cache Problems
To clear the cache before each query, try:
10 Gb or above:
Alter system flush buffer_cache;
9i:
Alter session set events 'immediate trace name flush_cache ';
