SQL Tuning 基础概述08 - SQL Tuning Advisor

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.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 => 'CRNOP',

 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.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.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：

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



PL/SQL procedure successfully completed.