初次使用SQL调优建议工具--SQL Tuning Advisor

在10g中，Oracle推出了自己的SQL优化辅助工具: SQL优化器(SQL Tuning Advisor ：STA)，它是新的DBMS_SQLTUNE包。

使用STA一定要保证优化器是CBO模式下。可是我觉得使用这样的工具，仅适合全然不懂SQL的调优的人群，不要觉得工具能解决好问题。

SQL说究竟是表达的是一个业务，工具怎么可能理解业务。SQL调优还是要用autotrace,10046,10053,display_cursor这些优秀的工具做诊断。然后依据业务和所具备的oracle基础的知识进行调优，这是最好的方法。今天在这里玩这个工具仅仅是玩票。

1.创建数据。有益不建索引，然后做查询

SQL> create table test1 as select * from dba_objects;

SQL> create table test2 as select * from dba_objects;

SQL> exec dbms_stats.gather_table_stats(user,'test1');

SQL> exec dbms_stats.gather_table_stats(user,'test2');

SQL> set timing on

SQL> set autotrace traceonly

SQL> select count(*) from test1 t1, test2 t2 where t1.object_id = t2.object_id;

已用时间:  00: 00: 00.07

运行计划

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

Plan hash value: 2544416891

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

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

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

|   0 | SELECT STATEMENT    |       |     1 |    10 |   298   (1)| 00:00:04 |

|   1 |  SORT AGGREGATE     |       |     1 |    10 |            |          |

|*  2 |   HASH JOIN         |       | 50981 |   497K|   298   (1)| 00:00:04 |

|   3 |    TABLE ACCESS FULL| TEST1 | 50982 |   248K|   149   (1)| 00:00:02 |

|   4 |    TABLE ACCESS FULL| TEST2 | 50983 |   248K|   149   (1)| 00:00:02 |

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

Predicate Information (identified by operation id):

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

   2 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")

统计信息

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

          1  recursive calls

          0  db block gets

       1410  consistent gets

          0  physical reads

          0  redo size

        410  bytes sent via SQL*Net to client

        385  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

SQL> set autotrace off





2.通过DBMS_SQLTUNE包的CREATE_TUNING_TASK来创建一个优化任务。然后通过DBMS_SQLTUNE.EXECUTE_TUNING_TASK来运行调优任务，生成调优建议。

SQL> DECLARE

       my_task_name VARCHAR2(300);

       my_sqltext   CLOB;

     BEGIN

       my_sqltext := 'select count(*) from test1 t1, test2 t2 where t1.object_id = t2.object_id';

       my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK(

               sql_text    => my_sqltext,

               user_name   => 'TEST',   -- 必须大写

               scope       => 'COMPREHENSIVE',

               time_limit  => 10,

               task_name   => 'tuning_sql_test',

               description => 'Task to tune a query on a specified table');

       DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name => 'tuning_sql_test');

     END;

/



官方文档解析：

sql_text     The text of a SQL statement

user_name    The username for whom the statement is to be tuned

scope        Tuning scope (limited/comprehensive)

time_limit   The maximum duration in seconds for the tuning session

task_name    An optional tuning task name

description  A task of the SQL tuning session to a maximum of 256 characters

          

3.检查优化任务的状态          

SQL> select task_name,ADVISOR_NAME,STATUS from  user_advisor_tasks;

TASK_NAME                      ADVISOR_NAME                   STATUS

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

tuning_sql_test                SQL Tuning Advisor             COMPLETED



4.查看优化结果

SQL> set LONGCHUNKSIZE 999999

SQL> set serveroutput on size 999999

SQL> set long 999999

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

DBMS_SQLTUNE.REPORT_TUNING_TASK('TUNING_SQL_TEST')

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

GENERAL INFORMATION SECTION

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

Tuning Task Name                  : tuning_sql_test

Tuning Task Owner                 : TEST

Scope                             : COMPREHENSIVE

Time Limit(seconds)               : 10

Completion Status                 : COMPLETED

Started at                        : 05/23/2014 08:50:40

Completed at                      : 05/23/2014 08:50:41

Number of Index Findings          : 1

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

Schema Name: TEST

SQL ID     : afjq3us3nf5dt

SQL Text   : select count(*) from test1 t1, test2 t2 where t1.object_id =

             t2.object_id

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

FINDINGS SECTION (1 finding)

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

1- Index Finding (see explain plans section below)

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

通过创建一个或多个索引能够

  Recommendation (estimated benefit: 100%)

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

  -考虑执行能够改进物理方案设计的 Access Advi

    create index TEST.IDX$$_0C890001 on TEST.TEST1('OBJECT_ID');



  -考虑执行能够改进物理方案设计的 Access Advi

    create index TEST.IDX$$_0C890002 on TEST.TEST2('OBJECT_ID');



  Rationale

  ---------

创建推荐的索引能够显著地改进此语句的运行计划。

可是, 使用典型的

 可能比单个语句更可取。通过这样的方法能够获得全面的索引建

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

EXPLAIN PLANS SECTION

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

1- Original

-----------

Plan hash value: 2544416891

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

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

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

|   0 | SELECT STATEMENT    |       |     1 |    10 |   298   (1)| 00:00:04 |

|   1 |  SORT AGGREGATE     |       |     1 |    10 |            |          |

|*  2 |   HASH JOIN         |       | 50981 |   497K|   298   (1)| 00:00:04 |

|   3 |    TABLE ACCESS FULL| TEST1 | 50982 |   248K|   149   (1)| 00:00:02 |

|   4 |    TABLE ACCESS FULL| TEST2 | 50983 |   248K|   149   (1)| 00:00:02 |

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

Predicate Information (identified by operation id):

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

   2 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")



2- Using New Indices

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

Plan hash value: 3060659111

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

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

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

|   0 | SELECT STATEMENT       |                |     1 |    10 |    53   (2)| 00:00:01 |

|   1 |  SORT AGGREGATE        |                |     1 |    10 |            |          |

|*  2 |   HASH JOIN            |                | 50981 |   497K|    53   (2)| 00:00:01 |

|   3 |    INDEX FAST FULL SCAN| IDX$$_0C890001 | 50982 |   248K|    26   (0)| 00:00:01 |

|   4 |    INDEX FAST FULL SCAN| IDX$$_0C890002 | 50983 |   248K|    26   (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

   2 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")

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

5.验证一下

依据advisor的建议进行调优，1410降到204，是乎有点效果。

SQL>create index ind_t1_object_id  on test1(object_id);

SQL> create index ind_t2_object_id  on test2(object_id);

SQL> set autotrace traceonly

SQL> select count(*) from test1 t1, test2 t2 where t1.object_id = t2.object_id;

已用时间:  00: 00: 00.06

运行计划

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

Plan hash value: 1069114244

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

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

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

|   0 | SELECT STATEMENT       |                  |     1 |    10 |    51   (2)| 00:00:01 |

|   1 |  SORT AGGREGATE        |                  |     1 |    10 |            |          |

|*  2 |   HASH JOIN            |                  | 50981 |   497K|    51   (2)| 00:00:01 |

|   3 |    INDEX FAST FULL SCAN| IND_T1_OBJECT_ID | 50982 |   248K|    25   (0)| 00:00:01 |

|   4 |    INDEX FAST FULL SCAN| IND_T2_OBJECT_ID | 50983 |   248K|    25   (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

   2 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")

统计信息

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

          1  recursive calls

          0  db block gets

        240  consistent gets

        226  physical reads

          0  redo size

        410  bytes sent via SQL*Net to client

        385  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          1  rows processed

6.删除优化任务

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