Oracle SQL执行计划基线总结（SQL Plan Baseline）継続

八、迁移基线

dbms_spm提供了多个过程来在数据库之间迁移SQL计划基线

1. create_stgtab_baseline创建一个计划基线保存表
2. pack_stgtab_baseline将基线从数据字典复制到第一步的表中
3. unpack_stgtab_baseline将基线从保存表中复制到迁移数据库的数据字典中

大概过程如下：

1、创建一张保存数据字典中基线表内容的用户表

exec dbms_spm.create_stgtab_baseline(table_name => 'BASELINE_TEST',table_owner => 'SCOTT',tablespace_name =>'');

2、将数据字典中基线表的内容 插入到 第一步创建的用户表中

exec :i := dbms_spm.pack_stgtab_baseline(table_name => 'BASELINE_TEST', table_owner => 'SCOTT');

备注：可以支持多种方式插入,例如包含特定字符的SQL相关的基线，sql_handle来精确识别一个基线，具体见文档

3、通过迁移工具迁移用户表

exp/imp or expdp/impdp

4、将迁移过来的用户表中保存的基线内容 插入到当前库的数据字典中，从而实现迁移

exec :i := dbms_spm.unpack_stgtab_baseline(table_name => 'BASELINE_TEST',table_owner => 'SCOTT');

备注：可以支持多种方式，与步骤2一样，具体见文档

 

九、删除基线

1. 可以通过dbms_SPM.drop_sql_plan_baseline包来手工删除数据字典里的基线
2. 为使用的基线，fixed为no的基线，将在一定的保留期后自动删除(可查看dba_sql_management_config视图）

手工删除方法如下

SET SERVEROUTPUT ON

DECLARE

v_text PLS_INTEGER;

BEGIN

v_text := DBMS_SPM.drop_sql_plan_baseline(sql_handle => 'SYS_SQL_7b76323ad90440b9',plan_name => NULL);

DBMS_OUTPUT.put_line(v_text);

END;

/

 

十、将一个SQL语句固定为我们期望的执行计划

我一般通过如下几步实现（仅供参考）

1、为这个SQL语句创建基线

2、给这个SQL语句添加hint赖宇星，确保SQL语句添加hint后的执行计划与我们期望一样

3、将第2步产生的执行计划，添加到第一步创建的基线中（注意，前面已经说过，一个SQL语句可以有多个基线！）

4、删除基线中第1步创建的那个执行计划（这样，我们就可以确保基线中只有我们期望的执行计划，即保存第2步SQL语句的执行计划）

5、验证是否生效

后续有示例，加深理解！

 

十一、示例（将一个SQL语句固定为我们期望的执行计划）

首先运行两个结构相同的语句，下面的实验通过SQL计划基线，将一个语句的执行计划通过另一个语句的执行计划来固定

SQL> select sql_handle,plan_name,dbms_lob.substr(sql_text,60,1) sql_text,ACCEPTED from dba_sql_plan_baselines;

未选定行

SQL> alter system flush shared_pool;

系统已更改。

SQL> select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where id=711;

ID NAME TYPE

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

711 I_STREAMS_PROCESS_PARAMS1 INDEX

SQL> select /* outlinetest3 */ /*+ index(dh_stat) */ * from dh_stat where id=711;

ID NAME TYPE

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

711 I_STREAMS_PROCESS_PARAMS1 INDEX

 

SQL> select sql_text,sql_id,hash_value,child_number,plan_hash_value,to_char(LAST_ACTIVE_TIME,'hh24:mi:ss') time

2 from v$sql a where sql_text like '%outlinetest%' and sql_text not like '%v$sql%';

SQL_TEXT SQL_ID HASH_VALUE CHILD_NUMBER PLAN_HASH_VALUE TIME

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

select /* outlinetest2 */ /*+ full(dh_stat) */ * from d 4vaj9fgjysy9c 3823925548 0 1845196118 12:27:31

h_stat where id=711

select /* outlinetest3 */ /*+ index(dh_stat) */ * from fm35jcmypb3qu 4250242778 0 2780970545 12:27:41

dh_stat where id=711

 

SQL> select * from table(dbms_xplan.display_cursor('4vaj9fgjysy9c','',''));

PLAN_TABLE_OUTPUT

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

SQL_ID 4vaj9fgjysy9c, child number 0

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

select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where

id=711

Plan hash value: 1845196118

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

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

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

| 0 | SELECT STATEMENT | | | | 124 (100)| |

|* 1 | TABLE ACCESS FULL| DH_STAT | 1 | 38 | 124 (1)| 00:00:02 |

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

Predicate Information (identified by operation id):

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

1 - filter("ID"=711)

已选择19行。

 

SQL> select * from table(dbms_xplan.display_cursor('fm35jcmypb3qu','',''));

PLAN_TABLE_OUTPUT

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

SQL_ID fm35jcmypb3qu, child number 0

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

select /* outlinetest3 */ /*+ index(dh_stat) */ * from dh_stat where

id=711

Plan hash value: 2780970545

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

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

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

| 0 | SELECT STATEMENT | | | | 2 (100)| |

| 1 | TABLE ACCESS BY INDEX ROWID| DH_STAT | 1 | 38 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | IND_1 | 1 | | 1 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

2 - access("ID"=711)

已选择20行。

 

 

SQL> DECLARE

2 k1 pls_integer;

3 begin

4 k1 := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE (

5 sql_id=>'4vaj9fgjysy9c',

6 plan_hash_value=>1845196118

7 );

8 end;

9 /

PL/SQL 过程已成功完成。

 

SQL> select sql_handle,plan_name,dbms_lob.substr(sql_text,60,1) sql_text,ACCEPTED from dba_sql_plan_baselines;

 

SQL_HANDLE PLAN_NAME SQL_TEXT ACC

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

SYS_SQL_11bcd50cd51504e9 SQL_PLAN_13g6p1maja17934f41c8d select /* outlinetest2 */ /*+ full(dh_stat) */ * from d YES

h_sta

 

刚生产sql plan baseline的时候，第一次查询，无法找到执行计划，直到第二次执行的时候，才能看到，如下

SQL> select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where id=711;

ID NAME TYPE

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

711 I_STREAMS_PROCESS_PARAMS1 INDEX

SQL> select * from table(dbms_xplan.display_cursor('4vaj9fgjysy9c','',''));

PLAN_TABLE_OUTPUT

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

SQL_ID: 4vaj9fgjysy9c cannot be found

SQL> select sql_text,sql_id,hash_value,child_number,plan_hash_value,to_char(LAST_ACTIVE_TIME,'hh24:mi:ss') time

2 from v$sql a where sql_text like '%outlinetest%' and sql_text not like '%v$sql%';

SQL_TEXT SQL_ID HASH_VALUE CHILD_NUMBER PLAN_HASH_VALUE TIME

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

select /* outlinetest3 */ /*+ index(dh_stat) */ * from fm35jcmypb3qu 4250242778 0 2780970545 12:27:41

dh_stat where id=711

 

 

SQL> select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where id=711;

ID NAME TYPE

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

711 I_STREAMS_PROCESS_PARAMS1 INDEX

SQL> select sql_text,sql_id,hash_value,child_number,plan_hash_value,to_char(LAST_ACTIVE_TIME,'hh24:mi:ss') time

2 from v$sql a where sql_text like '%outlinetest%' and sql_text not like '%v$sql%';

 

SQL_TEXT SQL_ID HASH_VALUE CHILD_NUMBER PLAN_HASH_VALUE TIME

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

select /* outlinetest2 */ /*+ full(dh_stat) */ * from d 4vaj9fgjysy9c 3823925548 0 1845196118 12:30:54

h_stat where id=711

select /* outlinetest3 */ /*+ index(dh_stat) */ * from fm35jcmypb3qu 4250242778 0 2780970545 12:27:41

dh_stat where id=711

 

 

SQL> select * from table(dbms_xplan.display_cursor('4vaj9fgjysy9c','',''));

PLAN_TABLE_OUTPUT

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

SQL_ID 4vaj9fgjysy9c, child number 0

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

select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where

id=711

 

Plan hash value: 1845196118

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

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

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

| 0 | SELECT STATEMENT | | | | 124 (100)| |

|* 1 | TABLE ACCESS FULL| DH_STAT | 1 | 38 | 124 (1)| 00:00:02 |

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

Predicate Information (identified by operation id):

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

 

1 - filter("ID"=711)

Note

-----

- SQL plan baseline SQL_PLAN_13g6p1maja17934f41c8d used for this statement

已选择23行。

 

将符合我们预期的执行计划的加载到第一次生成的sql baseline中！

SQL> DECLARE

2 k1 pls_integer;

3 begin

4 k1 := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE (

5 sql_id=>'fm35jcmypb3qu',

6 plan_hash_value=>2780970545,sql_handle=>'SYS_SQL_11bcd50cd51504e9'

7 );

8 end;

9 /

 

PL/SQL 过程已成功完成。

 

可以看到，SYS_SQL_11bcd50cd51504e9下目前有两个plan_name

SQL> select sql_handle,plan_name,dbms_lob.substr(sql_text,60,1) sql_text,ACCEPTED from dba_sql_plan_baselines;

 

SQL_HANDLE PLAN_NAME SQL_TEXT ACC

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

SYS_SQL_11bcd50cd51504e9 SQL_PLAN_13g6p1maja1790cce5f0e select /* outlinetest2 */ /*+ full(dh_stat) */ * from d YES

h_sta

 

SYS_SQL_11bcd50cd51504e9 SQL_PLAN_13g6p1maja17934f41c8d select /* outlinetest2 */ /*+ full(dh_stat) */ * from d YES

h_sta

删除第一个plan_name，即将我们不需要的执行计划版本去除掉！

SQL> DECLARE

2 k1 pls_integer;

3 begin

4 k1 := DBMS_SPM.drop_sql_plan_baseline ( sql_handle=>'SYS_SQL_11bcd50cd51504e9',plan_name=>'SQL_PLAN_13g6p1maja17934f41c8d');

5 end;

6 /

 

PL/SQL 过程已成功完成。

 

 

 

通过下面的一部分测试，我们可以看到，新的SQL计划基线已经正常生效，及时语句中包含full提示，执行计划也走索引定位数据

SQL> select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where id=711;

ID NAME TYPE

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

711 I_STREAMS_PROCESS_PARAMS1 INDEX

 

SQL> select * from table(dbms_xplan.display_cursor('4vaj9fgjysy9c','',''));

PLAN_TABLE_OUTPUT

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

SQL_ID 4vaj9fgjysy9c, child number 1

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

select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where

id=711

Plan hash value: 2780970545

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

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

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

| 0 | SELECT STATEMENT | | | | 2 (100)| |

| 1 | TABLE ACCESS BY INDEX ROWID| DH_STAT | 1 | 38 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | IND_1 | 1 | | 1 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

2 - access("ID"=711)

Note

-----

- SQL plan baseline SQL_PLAN_13g6p1maja1790cce5f0e used for this statement

已选择24行。

 

 

可以通过dba_sql_plan_baselines来显示可用的SQL计划基线的一般信息，也可以通过如下这种方式显示执行SQL计划基线的详细信息！

select * from table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SYS_SQL_11bcd50cd51504e9',plan_name=>'SQL_PLAN_13g6p1maja1790cce5f0e'));

 

PLAN_TABLE_OUTPUT

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

SQL handle: SYS_SQL_11bcd50cd51504e9

SQL text: select /* outlinetest2 */ /*+ full(dh_stat) */ * from dh_stat where

id=711

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

 

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

Plan name: SQL_PLAN_13g6p1maja1790cce5f0e Plan id: 214851342

Enabled: YES Fixed: NO Accepted: YES Origin: MANUAL-LOAD

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

 

Plan hash value: 2780970545

 

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

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

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

| 0 | SELECT STATEMENT | | 1 | 38 | 2 (0)| 00:00:01 |

| 1 | TABLE ACCESS BY INDEX ROWID| DH_STAT | 1 | 38 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | IND_1 | 1 | | 1 (0)| 00:00:01 |

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

 

Predicate Information (identified by operation id):

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

 

2 - access("ID"=711)

已选择26行。

 

查看SQL计划基线中保存的hint提示集合

SQL> conn /as sysdba

已连接。

SQL> select

2 extractvalue(value(d), '/hint') as outline_hints

3 from

4 xmltable('/outline_data/hint'

5 passing (

6 select

7 xmltype(comp_data) as xmlval

8 from

9 sqlobj$data sod, sqlobj$ so

10 where so.signature = sod.signature

11 and so.plan_id = sod.plan_id

12 and comp_data is not null

13 and name like '&baseline_plan_name'

14 )

15 ) d;

输入 baseline_plan_name 的值: SQL_PLAN_13g6p1maja1790cce5f0e

原值 13: and name like '&baseline_plan_name'

新值 13: and name like 'SQL_PLAN_13g6p1maja1790cce5f0e'

 

OUTLINE_HINTS

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

IGNORE_OPTIM_EMBEDDED_HINTS

OPTIMIZER_FEATURES_ENABLE('11.2.0.1')

DB_VERSION('11.2.0.1')

ALL_ROWS

OUTLINE_LEAF(@"SEL$1")

INDEX_RS_ASC(@"SEL$1" "DH_STAT"@"SEL$1" ("DH_STAT"."ID"))

 

已选择6行。

更多Oracle相关信息见Oracle 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=12

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