[20190214]11g Query Result Cache RC Latches补充.txt

[20190214]11g Query Result Cache RC Latches补充.txt

--//上午测试链接:http://blog.itpub.net/267265/viewspace-2632907/
--//发现自己的一个错误,另外写一篇帖子更正.
--//顺便复习result cache的相关内容:链接:https://blog.csdn.net/jolly10/article/details/81382644

查看SQL结果高速缓存字典信息
(G)V$RESULT_CACHE_STATISTICS : 列出各种高速缓存设置和内存使用量统计信息
(G)V$RESULT_CACHE_MEMORY : 列出所有内存块和相应的统计信息
(G)V$RESULT_CACHE_OBJECTS: 列出所有对象（高速缓存结果和依赖性）及其属性
(G)V$RESULT_CACHE_DEPENDENCY: 列出高速缓存结果之间的依赖性详细信息及依赖性

dbms_result_cache包可以监视和管理result cache

例如:
dbms_result_cache.flush：清除result cache。
dbms_result_cache.invalidate(owner,name)：使某对象的result cache无效。
dbms_result_cache.status：显示result cache的状态。
dbms_result_cache.memory_report：显示result cache的内存使用状况。

1.环境:
SCOTT@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SCOTT@book> create table job_times ( sid   number, time_ela number);
Table created.

SCOTT@book> create table hc_t ( n number(*,0), v varchar2(200)) ;
Table created.

SCOTT@book> insert into hc_t select level, dbms_random.string('p', 200) from dual connect by level <= 10000;
10000 rows created.

SCOTT@book> create unique index i_hc_t on hc_t(n);
Index created.

SCOTT@book> commit;
Commit complete.

--//分析表略.

create or replace procedure do_rc(
 p_iterations in number,p_max in number
) is
 l_rowid  rowid;
 l_n number;
begin
 insert into job_times
  values (sys_context('userenv', 'sid'), dbms_utility.get_time)
  returning rowid into l_rowid;

for i in 1 .. p_iterations
 loop
  l_n:=trunc(dbms_random.value(1, p_max));
  for cur in (select /*+ result_cache */ * from hc_t where n=l_n)
  loop
   null;
  end loop;
 end loop;

update job_times set
   time_ela=dbms_utility.get_time-time_ela
  where rowid=l_rowid;
end;
/
--//注:我加入参数p_max,限制取值范围.
--//为了重复测试建立脚本.
$ cat aa.sql
delete from job_times;
Commit ;

declare
 l_job number;
begin
 for i in 1 .. 4
 loop
  dbms_job.submit(
   job => l_job,
   what => 'do_rc(100000,&&1);'
    );
 end loop;
end;
/
commit ;

2.开始测试:
SCOTT@book> show parameter result
NAME                                 TYPE         VALUE
------------------------------------ ------------ ----------
client_result_cache_lag              big integer  3000
client_result_cache_size             big integer  0
result_cache_max_result              integer      5
result_cache_max_size                big integer  1792K
result_cache_mode                    string       MANUAL
result_cache_remote_expiration       integer      0

SCOTT@book> exec dbms_result_cache.flush()
PL/SQL procedure successfully completed.

SCOTT@book> set serverout on
SCOTT@book> exec dbms_result_cache.memory_report
R e s u l t   C a c h e   M e m o r y   R e p o r t
[Parameters]
Block Size          = 0 bytes
Maximum Cache Size  = 0 bytes (0 blocks)
Maximum Result Size = 0 bytes (0 blocks)
[Memory]
Total Memory = 40568 bytes [0.022% of the Shared Pool]
... Fixed Memory = 40568 bytes [0.022% of the Shared Pool]
... Dynamic Memory = 0 bytes [0.000% of the Shared Pool]
PL/SQL procedure successfully completed.

--//我前面测试忽略的result cache的大小.

SCOTT@book> @ aa.sql 10000
4 rows deleted.
Commit complete.
PL/SQL procedure successfully completed.
Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;
  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)
---------- ------------- -------------
         4        4001.5         16006

--//以上我上午测试的结果.大约每个job需要40秒上下.

SCOTT@book> exec dbms_result_cache.memory_report
R e s u l t   C a c h e   M e m o r y   R e p o r t
[Parameters]
Block Size          = 1K bytes
Maximum Cache Size  = 1792K bytes (1792 blocks)
Maximum Result Size = 89K bytes (89 blocks)
[Memory]
Total Memory = 2003960 bytes [1.111% of the Shared Pool]
... Fixed Memory = 40568 bytes [0.022% of the Shared Pool]
... Dynamic Memory = 1963392 bytes [1.089% of the Shared Pool]
....... Overhead = 128384 bytes
....... Cache Memory = 1792K bytes (1792 blocks)
........... Unused Memory = 0 blocks
........... Used Memory = 1792 blocks
............... Dependencies = 1 blocks (1 count)
............... Results = 1791 blocks
................... SQL     = 1791 blocks (1791 count)
PL/SQL procedure successfully completed.

--//实际上我的环境仅仅能容纳1791个结果.也就是我的配置太小,共享池不够大.result_cache_max_result=5,仅仅使用共享池的5%.

SCOTT@book> @ aa.sql 1791
4 rows deleted.
Commit complete.
PL/SQL procedure successfully completed.
Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;
  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)
---------- ------------- -------------
         4         440.5          1762

--//你可以发现这个就与没有做result cache的结果相近了.
--//我重启数据库.通过result cache :RC latch记数也可以验证这个问题.

SCOTT@book> column name format a30
SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';
NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME
------------------------------ ---------- ---------- ---------- ----------
Result Cache: RC Latch                  0          0          0          0
Result Cache: SO Latch                  0          0          0          0
Result Cache: MB Latch                  0          0          0          0

SCOTT@book> @ aa.sql 1791
4 rows deleted.
Commit complete.
PL/SQL procedure successfully completed.
Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;
  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)
---------- ------------- -------------
         4           432          1728

SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';
NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME
------------------------------ ---------- ---------- ---------- ----------
Result Cache: RC Latch             405177       3865         10        132
Result Cache: SO Latch                  8          0          0          0
Result Cache: MB Latch                  0          0          0          0

SCOTT@book> @ aa.sql 10000
4 rows deleted.
Commit complete.
PL/SQL procedure successfully completed.
Commit complete.

SCOTT@book> select count(*),avg(TIME_ELA),sum(TIME_ELA) from job_times ;
  COUNT(*) AVG(TIME_ELA) SUM(TIME_ELA)
---------- ------------- -------------
         4       3978.25         15913

SCOTT@book> select name, gets, misses, sleeps, wait_time from v$latch where name like 'Result Cache%';
NAME                                 GETS     MISSES     SLEEPS  WAIT_TIME
------------------------------ ---------- ---------- ---------- ----------
Result Cache: RC Latch            1787843     534395     683654   67269002
Result Cache: SO Latch                 16          0          0          0
Result Cache: MB Latch                  0          0          0          0