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SQL Tuning 基础概述08 - SQL Tuning Advisor

2015-01-26 19:06 by AlfredZhao, ... 阅读, ... 评论, 收藏, 编辑

SQL调优顾问 SQL Tuning Advisor的使用案例:

1.构建测试表T

SQL> conn zjy/zjy
Connected.
SQL> create table t as select * from dba_objects;

Table created.
SQL> select count(*) from t;

COUNT(*)
----------
653500

2.定义调整任务

对“select owner, object_id, object_name from t where object_id=200000”这个sql定义调整任务:

declare 
tune_task_name varchar2(30);
bad_sql_stmt clob;
begin
 bad_sql_stmt := '';
 tune_task_name := dbms_sqltune.create_tuning_task
 (sql_text => bad_sql_stmt,
 user_name => 'ZJY',
 scope => 'COMPREHENSIVE',
 time_limit => 3600,
 task_name => 'zjy_sql_tuning_task',
 description => 'sql_tuning_advisor for this sql'
 ); 
end;
/

 

SQL> declare 
2 tune_task_name varchar2(30);
3 bad_sql_stmt clob;
4 begin
5 bad_sql_stmt := 'select owner, object_id, object_name from t where object_id=200000';
6 tune_task_name := dbms_sqltune.create_tuning_task
7 (sql_text => bad_sql_stmt,
8 user_name => 'ZJY',
9 scope => 'COMPREHENSIVE',
10 time_limit => 3600,
11 task_name => 'zjy_sql_tuning_task',
12 description => 'sql_tuning_advisor for this sql'
13 ); 
14 end;
15 /

PL/SQL procedure successfully completed.

3.修改调整任务参数

可以修改调整任务的一些参数,比如:

SQL> begin
2 dbms_sqltune.set_tuning_task_parameter
3 (task_name => 'zjy_sql_tuning_task',
4 parameter => 'TIME_LIMIT', value => 1800
5 );
6 end;
7 /

PL/SQL procedure successfully completed.

4.执行调整任务

开始执行调整任务:

begin
 dbms_sqltune.execute_tuning_task
 (task_name => 'zjy_sql_tuning_task');
end;
/

 

SQL> begin
2 dbms_sqltune.execute_tuning_task
3 (task_name => 'zjy_sql_tuning_task');
4 end;
5 /

PL/SQL procedure successfully completed.

5.监控调整任务

监控调整任务的执行状态:

select task_name, status, sofar, totalwork
 from dba_advisor_tasks
 join v$advisor_progress using(task_id)
 where task_name = 'zjy_sql_tuning_task';

 

SQL> select task_name, status, sofar, totalwork
2 from dba_advisor_tasks
3 join v$advisor_progress using(task_id)
4 where task_name = 'zjy_sql_tuning_task';

TASK_NAME STATUS SOFAR TOTALWORK
------------------------------ ----------- ---------- ----------
zjy_sql_tuning_task COMPLETED 1 1

6.查看调整任务建议

查看调整任务最终给出的建议:

SQL> select dbms_sqltune.report_tuning_task('zjy_sql_tuning_task') from dual;

DBMS_SQLTUNE.REPORT_TUNING_TASK('ZJY_SQL_TUNING_TASK')
-------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name : zjy_sql_tuning_task
Tuning Task Owner : ZJY
Workload Type : Single SQL Statement
Scope : COMPREHENSIVE
Time Limit(seconds): 1800
Completion Status : COMPLETED
Started at : 01/23/2015 14:58:40
Completed at : 01/23/2015 14:58:58

-------------------------------------------------------------------------------
Schema Name: ZJY
SQL ID : dmw0nx6g0b6h7
SQL Text : select owner, object_id, object_name from t where
object_id=200000

-------------------------------------------------------------------------------
FINDINGS SECTION (2 findings)
-------------------------------------------------------------------------------

1- Statistics Finding
---------------------
尚未分析表 "ZJY"."T"。

Recommendation
--------------
- 考虑收集此表的优化程序统计信息。
execute dbms_stats.gather_table_stats(ownname => 'ZJY', tabname => 'T',
estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt =>
'FOR ALL COLUMNS SIZE AUTO');

Rationale
---------
为了选择好的执行计划, 优化程序需要此表的最新统计信息。

2- Index Finding (see explain plans section below)
--------------------------------------------------
通过创建一个或多个索引可以改进此语句的执行计划。

Recommendation (estimated benefit: 99.86%)
------------------------------------------
- 考虑运行可以改进物理方案设计的访问指导或者创建推荐的索引。
create index ZJY.IDX$$_3EC90001 on ZJY.T("OBJECT_ID","OWNER","OBJECT_NAME")
;

Rationale
---------
创建推荐的索引可以显著地改进此语句的执行计划。但是, 使用典型的 SQL 工作量运行 "访问指导"
可能比单个语句更可取。通过这种方法可以获得全面的索引建议案, 包括计算索引维护的开销和附加的空间消耗。

-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------

1- Original
-----------
Plan hash value: 1601196873

--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 124 | 11904 | 3059 (1)| 00:00:37 |
|* 1 | TABLE ACCESS FULL| T | 124 | 11904 | 3059 (1)| 00:00:37 |
--------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - filter("OBJECT_ID"=200000)

2- Using New Indices
--------------------
Plan hash value: 3141638344

-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 96 | 4 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| IDX$$_3EC90001 | 1 | 96 | 4 (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - access("OBJECT_ID"=200000)

-------------------------------------------------------------------------------

7.删除调整任务

删除调整任务:

SQL> exec dbms_sqltune.drop_tuning_task('zjy_sql_tuning_task') ;

PL/SQL procedure successfully completed.