outline执行计划稳定使用


--1、创建表

create table a as select * from all_objects

update a set a.object_id=21 where object_id >=100;

commit;

create index a_inx on a(object_id);

begin

  dbms_stats.gather_table_stats('TEST','a');

end;

--2、

--iffs

variable i number

variable k number

execute :i:=20

execute :k:=21

select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

--实际iffs应该irs

execute :i:=22

execute :k:=25

select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

--验证实际带入变量值irs

select /*+gather_plan_statistics*/ count(*) from a where object_id between 22 and 25;

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

/*这里可以看到后续只要使用的绑定变量后续执行计划就都是iffs了除非该执行计划失效才会重新生成*/

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

--重新生成执行计划方法

/*

1、重新收集统计信息等待执行计划过期(默认"_optimizer_invalidation_period"过期时间5h)；

2、执行计划不在share pool(手动flush或age out等)

3、10.2.0.4后提供了个dbms_shared_pool.purge

4、对该表A做一个ddl操作,如添加一个注释comments   */

alter system flush shared_pool;

irs

execute :i:=22

execute :k:=25

select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

irs

execute :i:=20

execute :k:=21

select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

----以上可以看到大量数据还是走到irs这就是我们要的效果

----outline固定执行计划--------

--outline相关操作

--select * from dba_outlines  查看索引outline

--drop outline oltname  删除outline

--alter system set use_stored_outlines=ture; 禁用outline默认

--找到我们需要的绑定的执行计划

select sql_text, sql_id, hash_value, child_number

  from v$sql

 where sql_text like '%gather_plan_statistics%'

   and sql_text not like '%like%';

  

hash_value=913074179

child_number=0

--直接create outline需要用sql这里直接调用过程使用hash-value

--

begin

dbms_outln.create_outline('913074179','0');

end;

---

--查询已经生成

select * from dba_outlines

--让执outline生效默认是false

alter system set use_stored_outlines=ture;

---测试效果

--现在的执行计划是irs如果我们清除执行计划在使用21范围查询看结果

--如果结果是iffs那么就没有绑定成功

alter system flush shared_pool;

execute :i:=20

execute :k:=21

select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

PLAN_TABLE_OUTPUT

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

SQL_ID  085j460v6su03, child number 1

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

 select /*+gather_plan_statistics*/ count(*) from a where object_id between

:i and :k

Plan hash value: 2093133565

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

| Id  | Operation          | Name  | Starts | E-Rows | A-Rows |   A-Time   | Buf

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

|   1 |  SORT AGGREGATE    |       |      1 |      1 |      1 |00:00:00.10 |

|*  2 |   FILTER           |       |      1 |        |  49649 |00:00:00.01 |

|*  3 |    INDEX RANGE SCAN| A_INX |      1 |  49627 |  49649 |00:00:00.01 |

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

Predicate Information (identified by operation id):

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

   2 - filter(:I<=:K)

   3 - access("OBJECT_ID">=:I AND "OBJECT_ID"<=:K)

 

PLAN_TABLE_OUTPUT

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

Note

-----

   - outline "SYS_OUTLINE_14102216460808404" used for this statement

 

46 rows selected

------以上已经可以清楚看到outline已经生效执行计划里面也有提示

Note

-----

   - outline "SYS_OUTLINE_14102216460808404" used for this statement

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

--重启实例后该outline回到false失效需要手动启动或者做一个启动触发器每次启动自动执行

--同时启动outline和sqlprofile后会选择outline执行计划

--alter system set use_stored_outlines=ture;

SQL>

SQL> execute :i:=20

Warning: connection was lost and re-established

 

PL/SQL procedure successfully completed

i

---------

20

SQL> execute :k:=21

 

PL/SQL procedure successfully completed

k

---------

21

SQL> select /*+gather_plan_statistics*/ count(*) from a where object_id between :i and :k;

 

  COUNT(*)

----------

     49649

i

---------

20

k

---------

21

SQL> select * from table(dbms_xplan.display_cursor('085j460v6su03',null,'ALLSTATS LAST'));

 

PLAN_TABLE_OUTPUT

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

SQL_ID  085j460v6su03, child number 0

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

 select /*+gather_plan_statistics*/ count(*) from a where object_id between :i a

Plan hash value: 831184990

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

| Id  | Operation              | Name  | Starts | E-Rows | A-Rows |   A-Time   |

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

|   1 |  SORT AGGREGATE        |       |      1 |      1 |      1 |00:00:00.03 |

|*  2 |   FILTER               |       |      1 |        |  49649 |00:00:00.02 |

|*  3 |    INDEX FAST FULL SCAN| A_INX |      1 |  49627 |  49649 |00:00:00.02 |

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

Predicate Information (identified by operation id):

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

   2 - filter(:I<=:K)

   3 - filter(("OBJECT_ID"<=:K AND "OBJECT_ID">=:I))