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SQL Tuning 基础概述09 - SQL Access Advisor

2015-12-23 13:27  AlfredZhao  阅读(...)  评论(...编辑  收藏

Oracle官方文档对SQL Access Advisor的描述如下:

SQL Access Advisor, which is a tuning tool that provides advice on improving the performance of a database through partitioning, materialized views, indexes, and materialized view logs.

本文介绍下如何通过DBMS_ADVISOR的quick_tune过程使用SQL Access Advisor,当然,使用EM来执行SQL Access Advisor会更加方便。

  1. 构建测试表T1,T2
  2. 定义调整任务
  3. 创建调优脚本的目录
  4. 把调优脚本内容输出
  5. 查看调优脚本内容

1. 构建测试表T1,T2

-- 删除测试表
drop table t1 cascade constraints purge;
drop table t2 cascade constraints purge;
-- 创建测试表
create table t1( id number not null, n number, contents varchar2(4000) );
create table t2( id number not null, t1_id number not null, n number, contents varchar2(4000) );
-- 初始化测试数据
execute dbms_random.seed(0);
insert into t1  select rownum, rownum, dbms_random.string('a',50)   from dual   connect by level <= 1000   order by dbms_random.random;
commit;  

insert into t2  select rownum, rownum, rownum, dbms_random.string('b',60)  from dual  connect by level <= 100000  order by dbms_random.random;
commit;
-- 查询表数据量
select count(1) from t1;
select count(1) from t2;
-- 查询段大小
select segment_name, BYTES/1024/1024 "MB" from user_segments where segment_name in ('T1','T2');
-- 分析表(必须有统计信息)
analyze table t1 estimate statistics;
analyze table t2 estimate statistics;

测试SQL:

select * from t1, t2 where t1.id = t2.t1_id and t1.n = 19;

2. 定义调整任务

begin
 dbms_advisor.quick_tune
 (dbms_advisor.sqlaccess_advisor,
 'zjy_sql_access_task1',
 'select * from t1, t2 where t1.id = t2.t1_id and t1.n = 19'
 );
end;
/

3. 创建调优脚本的目录

create or replace directory tune_jy_scripts as '/tmp';

4. 把调优脚本内容输出

begin
 dbms_advisor.create_file
  (dbms_advisor.get_task_script('zjy_sql_access_task1'),
   'TUNE_JY_SCRIPTS',
   'zjy_sql_access_task_01.sql'
  );
end;
/

5. 查看调优脚本内容

more /tmp/zjy_sql_access_task_01.sql
Rem  SQL Access Advisor: Version 11.2.0.4.0 - Production
Rem  
Rem  Username:        JINGYU
Rem  Task:            zjy_sql_access_task1
Rem  Execution date:   
Rem  

CREATE INDEX "JINGYU"."T1_IDX$$_02330000"
    ON "JINGYU"."T1"
    ("N")
    COMPUTE STATISTICS;

CREATE INDEX "JINGYU"."T2_IDX$$_02330001"
    ON "JINGYU"."T2"
    ("T1_ID")
    COMPUTE STATISTICS;

可以看到这里给出的优化建议,在这里还是很准确的。
即:驱动表T1的限制条件列创建索引;被驱动表的连接条件创建索引。

6. 删除任务

exec dbms_sqltune.drop_tuning_task('zjy_sql_access_task1');