Oracle10g新特性：使用DBMS_SQLTUNE优化SQL

在Oracle10g之前，优化SQL是个比较费力的技术活，不停的分析执行计划，加hint，分析统计信息等等，当然也有SQL调优辅助工具可以使用，只是要么价格昂贵，要么效果不佳。在10g中，Oracle推出了自己的SQL优化辅助工具，这就是新的DBMS_SQLTUNE包。执行DBMS_SQLTUNE包进行sql优化需要有advisor的权限：

SYS@ning>grant advisor to ning;

Grant succeeded.

使用DBMS_SQLTUNE包进行SQL优化，大致可以分为四个步骤：

创建优化任务 执行优化任务 显示优化任务的结果 按照建议执行优化

一、创建优化任务

使用dbms_sqltune.create_tuning_task函数来创建优化任务，该参数的声明如下：

FUNCTION CREATE_TUNING_TASK RETURNS VARCHAR2

Argument Name Type In/Out Default?

SQLSET_NAME VARCHAR2 IN

BASIC_FILTER VARCHAR2 IN DEFAULT

OBJECT_FILTER VARCHAR2 IN DEFAULT

RANK1 VARCHAR2 IN DEFAULT

RANK2 VARCHAR2 IN DEFAULT

RANK3 VARCHAR2 IN DEFAULT

RESULT_PERCENTAGE NUMBER IN DEFAULT

RESULT_LIMIT NUMBER IN DEFAULT

SCOPE VARCHAR2 IN DEFAULT

TIME_LIMIT NUMBER IN DEFAULT

TASK_NAME VARCHAR2 IN DEFAULT

DESCRIPTION VARCHAR2 IN DEFAULT

PLAN_FILTER VARCHAR2 IN DEFAULT

SQLSET_OWNER VARCHAR2 IN DEFAULT

具体每个参数的含义请参考Oracle官方文档的说明。函数的返回值为创建的任务名。下面我们创建一个叫sql_tuning_test的任务：

NING@ning>DECLARE

2 my_task_name VARCHAR2 (30);

3 my_sqltext CLOB;

4 BEGIN

5 my_sqltext := ‘SELECT e.last_name, d.department_name, d.department_id

6 FROM employees e, departments d

7 WHERE e.department_id = d.department_id

8 AND d.department_id = :bnd’;

9 my_task_name := dbms_sqltune.create_tuning_task (sql_text=> my_sqltext,

10 bind_list => sql_binds (anydata.convertnumber (9)),

11 user_name => ‘NING’,

12 scope => ‘COMPREHENSIVE’,

13 time_limit => 60,

14 task_name => ‘sql_tuning_test’,

15 description => ‘Tuning Task’

16 );

17 END;

18 /

PL/SQL procedure successfully completed.

二、执行优化任务

通过调用dbms_sqltune.execute_tuning_task过程来执行前面创建好的优化任务。

PROCEDURE EXECUTE_TUNING_TASK

Argument Name Type In/Out Default?

—————– ————- —— ——–

TASK_NAME VARCHAR2 IN

NING@ning>exec dbms_sqltune.execute_tuning_task(‘sql_tuning_test’);

PL/SQL procedure successfully completed.

三、检查优化任务的状态

通过查看user_advisor_tasks/dba_advisor_tasks视图可以查看优化任务的当前状态。

NING@ning>SELECT status FROM USER_ADVISOR_TASKS WHERE task_name = ‘sql_tuning_test’;

STATUS

———–

COMPLETED

四、得到优化任务执行的结果

通过dbms_sqltune.report_tning_task函数可以获得优化任务的结果。

NING@ning>SET LONG 999999

NING@ning>set serveroutput on size 999999

NING@ning>SET LINESIZE 100

NING@ning>SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK(‘sql_tuning_test’) FROM DUAL;

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

——————————————————————————-

GENERAL INFORMATION SECTION

——————————————————————————-

Tuning Task Name : sql_tuning_test

Tuning Task Owner : NING

Scope : COMPREHENSIVE

Time Limit(seconds) : 60

Completion Status : COMPLETED

Started at : 04/30/2007 10:42:48

Completed at : 04/30/2007 10:42:49

Number of Statistic Findings : 2

Number of SQL Profile Findings : 1

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

——————————————————————————-

——————————————————————————-

Schema Name: NING

SQL ID : 6rbh5v8smjpdq

SQL Text : SELECT e.last_name, d.department_name, d.department_id

FROM employees e, departments d

WHERE e.department_id = d.department_id

AND d.department_id = :bnd

——————————————————————————-

FINDINGS SECTION (3 findings)

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

——————————————————————————-

——————————————————————————-

1- Statistics Finding

———————

Table “NING”.”DEPARTMENTS” was not analyzed.

Recommendation

————–

– Consider collecting optimizer statistics for this table.

execute dbms_stats.gather_table_stats(ownname => ‘NING’, tabname =>

‘DEPARTMENTS’, estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,

method_opt => ‘FOR ALL COLUMNS SIZE AUTO’);

Rationale

———

The optimizer requires up-to-date statistics for the table in order to

select a good execution plan.

2- Statistics Finding

———————

Table “NING”.”EMPLOYEES” was not analyzed.

Recommendation

————–

– Consider collecting optimizer statistics for this table.

execute dbms_stats.gather_table_stats(ownname => ‘NING’, tabname =>

‘EMPLOYEES’, estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,

method_opt => ‘FOR ALL COLUMNS SIZE AUTO’);

Rationale

———

The optimizer requires up-to-date statistics for the table in order to

select a good execution plan.

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

——————————————————————————-

3- SQL Profile Finding (see explain plans section below)

——————————————————–

A potentially better execution plan was found for this statement.

Recommendation (estimated benefit<=10%)

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

- Consider accepting the recommended SQL profile.

execute dbms_sqltune.accept_sql_profile(task_name => ‘sql_tuning_test’,

replace => TRUE);

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

——————————————————————————

——————————————————————————-

EXPLAIN PLANS SECTION

——————————————————————————-

1- Original With Adjusted Cost

——————————

Plan hash value: 2052257371

———————————————————————————-

| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |

———————————————————————————-

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

———————————————————————————–

| 0 | SELECT STATEMENT | | 1 | 26 | 22 (5)| 00:00:01 |

|* 1 | HASH JOIN | | 1 | 26 | 22 (5)| 00:00:01 |

|* 2 | TABLE ACCESS FULL| DEPARTMENTS | 1 | 7 | 3 (0)| 00:00:01 |

|* 3 | TABLE ACCESS FULL| EMPLOYEES | 1 | 19 | 18 (0)| 00:00:01 |

———————————————————————————-

Predicate Information (identified by operation id):

—————————————————

1 – access(“E”.”DEPARTMENT_ID”=”D”.”DEPARTMENT_ID”)

2 – filter(“D”.”DEPARTMENT_ID”=:BND)

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

———————————————————————————

3 – filter(“E”.”DEPARTMENT_ID”=:BND)

2- Using SQL Profile

——————–

Plan hash value: 1782137809

———————————————————————————-

| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |

———————————————————————————-

| 0 | SELECT STATEMENT | | 1 | 26 | 22 (5)| 00:00:01 |

|* 1 | HASH JOIN | | 1 | 26 | 22 (5)| 00:00:01 |

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

———————————————————————————-

|* 2 | TABLE ACCESS FULL| EMPLOYEES | 1 | 19 | 18 (0)| 00:00:01 |

|* 3 | TABLE ACCESS FULL| DEPARTMENTS | 1 | 7 | 3 (0)| 00:00:01 |

———————————————————————————-

Predicate Information (identified by operation id):

—————————————————

1 – access(“E”.”DEPARTMENT_ID”=”D”.”DEPARTMENT_ID”)

2 – filter(“E”.”DEPARTMENT_ID”=:BND)

3 – filter(“D”.”DEPARTMENT_ID”=:BND)

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘SQL_TUNING_TEST’)

然后我们就可以根据Recommendation部分的建议来执行优化操作了。

五、删除优化任务

通过调用dbms_sqltuen.drop_tuning_task可以删除已经存在的优化任务

NING@ning>exec dbms_sqltune.drop_tuning_task(‘sql_tuning_test’);

PL/SQL procedure successfully completed.

转自：http://hi.baidu.com/hanbingxiaoshi/blog/item/3c0cbb02b29e2e1a4afb5127.html