由于物化视图定义为on commit导致update更新基表慢的解决方案
由于物化视图定义为on commit导致update更新基表慢的解决方案
以下是模拟和解决测试过程：
(模拟update慢的过程)
1、首先基于基表创建物化视图日志:
create materialized view log on scott.emp with rowid;
2、首先基于scott用户下emp创建物化视图：
create materialized view mv_emp
REFRESH FAST on commit
as
select * from scott.emp;
3、通过oracle 10046 查看update语句执行过程:
(1)sql>alter session set sql_trace=true;
(2)sql>alter session set tracefile_identifier='lzq';
(3)sql>alter session set events '10046 trace name context forever, level 1';
(4)sql>update scott.emp set sal=1450 where empno=7934;
(5)sql>alter session set events '10046 trace name context off';
(6)sql>show parameter user_dump_dest
(7)cd 到user_dump_dest查看trace文件被标识为lzq的trace 文件.
(8)格式化trace文件方便查看，tkprof prod2_ora_8623_lzq.trc prod2_ora_8623_lzq.out
(9)查看生成的prod2_ora_8623_lzq.out文件并查找跟物化视图mv_emp执行相关的信息见如下：
(生产环境中update一条语句真正执行的时间为1分多，而其中此处merger into "SCOTT"."MV_EMP" 占了1分左右
，而物化视图真正是给日报、月报、年报来用的跟客户沟通不用更新基表的时候就立即更新物化视图，物化视图
可以抛弃on commit时候就刷新，可以采取定时更新即可，从而可以避免update更新基表慢的问题。)
MERGE INTO "SCOTT"."MV_EMP" "SNA$" USING (SELECT CURRENT$."EMPNO",
CURRENT$."ENAME",CURRENT$."JOB",CURRENT$."MGR",CURRENT$."HIREDATE",
CURRENT$."SAL",CURRENT$."COMM",CURRENT$."DEPTNO" FROM (SELECT "EMP"."EMPNO"
"EMPNO","EMP"."ENAME" "ENAME","EMP"."JOB" "JOB","EMP"."MGR" "MGR",
"EMP"."HIREDATE" "HIREDATE","EMP"."SAL" "SAL","EMP"."COMM" "COMM",
"EMP"."DEPTNO" "DEPTNO" FROM "EMP" "EMP") CURRENT$, (SELECT DISTINCT
MLOG$."EMPNO" FROM "SCOTT"."MLOG$_EMP" MLOG$ WHERE "XID$$" = :1 AND
("DMLTYPE$$" != 'D')) LOG$ WHERE CURRENT$."EMPNO" = LOG$."EMPNO")"AV$" ON
("SNA$"."EMPNO" = "AV$"."EMPNO") WHEN MATCHED THEN UPDATE SET
"SNA$"."EMPNO" = "AV$"."EMPNO","SNA$"."ENAME" = "AV$"."ENAME","SNA$"."JOB" =
"AV$"."JOB","SNA$"."MGR" = "AV$"."MGR","SNA$"."HIREDATE" =
"AV$"."HIREDATE","SNA$"."SAL" = "AV$"."SAL","SNA$"."COMM" = "AV$"."COMM",
"SNA$"."DEPTNO" = "AV$"."DEPTNO" WHEN NOT MATCHED THEN INSERT
(SNA$."EMPNO",SNA$."ENAME",SNA$."JOB",SNA$."MGR",SNA$."HIREDATE",SNA$."SAL",
SNA$."COMM",SNA$."DEPTNO") VALUES (AV$."EMPNO",AV$."ENAME",AV$."JOB",
AV$."MGR",AV$."HIREDATE",AV$."SAL",AV$."COMM",AV$."DEPTNO")
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.01 0.08 2 20 5 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.01 0.08 2 20 5 1
(模拟update慢的解决方案：)
1、首先删除之前创建的物化视图(先做个备份)
drop MATERIALIZED VIEW mv_emp;
2、创建物化视图
CREATE MATERIALIZED VIEW mv_emp
AS SELECT * FROM scott.emp;
3、建立一个用来刷新物化视图的存储过程:
CREATE OR REPLACE PROCEDURE auto_refresh_mview_job_proc
AS
BEGIN
dbms_mview.REFRESH('mv_emp');
END;
4、用ORACLE 10g的scheduler每天12:00和19:00定期刷新物化视图(时间可以根据需求定义)
BEGIN
DBMS_SCHEDULER.CREATE_JOB(
job_name => 'auot_refresh_mview_job',
job_type => 'STORED_PROCEDURE',
job_action => 'scott.auto_refresh_mview_job_proc',
start_date => SYSDATE,
repeat_interval => 'FREQ=DAILY; BYHOUR=12,19',
enabled => TRUE,
comments => 'Refresh materialized view mv_emp'
);
END;
5、通过oracle 10046 查看update语句执行过程:
(1)sql>alter session set sql_trace=true;
(2)sql>alter session set tracefile_identifier='lzq';
(3)sql>alter session set events '10046 trace name context forever, level 1';
(4)sql>update scott.emp set sal=1450 where empno=7934;
(5)sql>alter session set events '10046 trace name context off';
(6)sql>show parameter user_dump_dest
(7)cd 到user_dump_dest查看trace文件被标识为lzq的trace 文件.
(8)格式化trace文件方便查看，tkprof prod2_ora_8623_lzq.trc prod2_ora_8623_lzq.out
(9)查看生成的prod2_ora_8623_lzq.out文件并查找报告中是否还存在MERGE INTO "SCOTT"."MV_EMP"更新物化视图的信息，
此时因为已经定时为定时刷新，从而可以提高update语句的时间，从而优化过程完成。
