稳定ORACLE的执行计划

时间  2019-11-12
标签 稳定 oracle 执行 计划 栏目 Oracle 繁體版
原文   原文链接

原文发表在:http://l4j.cc/2019/04/19/oracle-sql-plan-management/sql

 不少时候可能咱们都但愿CBO可以帮咱们生成正确、高效的执行计划，可是不少时候事实并不是如此，可能由于各类各样的缘由(如，统计信息不正确或者CBO天生的缺陷等)都会致使生成的执行计划特别的低效。以前的一家公司有一台专门用于批量作数据校验清洗的数据库，每次校验清洗完成数据就会清理掉，统计信息常常会发生较大的变动，以前跑得好好的SQL，可能有时候跑5-6个小时都跑不完了，这时候查看执行计划，发现不正确的统计信息致使了执行计划的变动。数据库

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 这时候咱们就但愿数据库中运行的SQL都能有正确、稳定的执行计划，在10g开始的版本中能够经过SQL Profile来稳定执行计划或者在不改变SQL的状况下修改执行计划。11g开始可使用偏主动的稳定执行计划的手段——SPM(SQL PLAN MANAGEMENT)，保证只有被验证过的执行计划才会被启用。ide

SQL Profile

 SQL Profile是包含特定于SQL语句的辅助统计信息的数据库对象，能够改进优化器基数估计，从而选择更好的执行计划。  当选择执行计划时优化器会考虑如下信息：函数

  1. SQL Profile提供的辅助统计信息
  2. 当时SQL的运行环境，如数据库配置，变量绑定，与优化器相关的统计信息等。

 因此，上面两个条件的任意一个发生变化，都有可能致使执行计划的改变。下面看下SQL Profile的一些基本操做以及如何在线进行SQL的调整。性能

accepting sql profile

 经过DBMS_SQLTUNE.ACCEPT_SQL_PROFILE存储过程能够接受一个SQL Profile，只有在咱们接受了一个SQL Profile以后，优化器才能使用他做为产生执行计划的输入。这个存储过程有两个比较重要的参数：测试

  • profile_type 这个参数用于控制是否改变并行执行行为，REGULAR_PROFILE 不更改成并行执行，PX_PROFLE 用于更改并行执行的SQL Profile。
  • force_match 该参数用于控制SQL语句匹配，有两个值——TRUE和FALSE。对于SQL语句中where条件的字面值，当force_match=TRUE时，会将其替换为变量绑定，因此当字面值不一样时也能够重用该SQL Profile。值为FALSE时，where条件的字面值则不会替换。

下面是ACCEPT_SQL_PROFILE的例子：优化

DECLARE
  my_sqlprofile_name VARCHAR2(30);
BEGIN
  my_sqlprofile_name := DBMS_SQLTUNE.ACCEPT_SQL_PROFILE ( 
    task_name    => 'STA_SPECIFIC_EMP_TASK'
,   name         => 'my_sql_profile'
,   profile_type => DBMS_SQLTUNE.PX_PROFILE
,   force_match  => true 
);
END;
/

Listing SQL Profile

 能够经过DBA_SQL_PROFILES数据字典视图来查看存储在数据库中的SQL Profile。this

SQL> SELECT NAME,CATEGORY,SQL_TEXT,FORCE_MATCHING,STATUS FROM DBA_SQL_PROFILES;

NAME                           CATEGORY   SQL_TEXT                  FOR STATUS
------------------------------ ---------- ------------------------- --- --------
SYS_SQLPROF_016986bccd640000   DEFAULT    select /*+ use_nl(a b) in NO  ENABLED
                                          dex(b) */a.brwyid,a.yljgd
                                          m,a.jzlsh,b.mzzddm from t
                                          est_e

Altering SQL Profile

 经过ALTER_SQL_PROFILE中的attribute_name参数能够修改SQL Profile相应的参数值。调试

BEGIN DBMS_SQLTUNE.ALTER_SQL_PROFILE ( 
   name            =>  'my_sql_profile'
,  attribute_name  =>  'FORCE_MATCH'
,  value           =>  'TRUE'      
);
END;
/

Droping SQL Profile

 经过DROP_SQL_PROFILE存储过程能够删除特定的SQL Profile

BEGIN
  DBMS_SQLTUNE.DROP_SQL_PROFILE ( 
    name => 'my_sql_profile' 
);
END;
/

经过SQL Profile调整线上SQL执行计划

 经过手工建立SQL Profile的方式，能够在不更改目标SQL的SQL文本的状况下修改SQL的执行计划，并且能够很好的稳定SQL的执行计划。  下面是手工建立SQL Profile的例子,在TEST_ENV.TB_TABLE_LIST的列TABLE_NAME上有一个名为IDX_TB_TABLE_LIST_TBNAME的B树索引： 一、首先加一个全表扫描的HINTS来执行下面的SQL，模拟线上的一个执行低效的SQL，并查看其执行计划。

SQL> SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
------------------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
SQL_ID  1a319c1c2b3rz, child number 0
-------------------------------------
SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 1475094007

-----------------------------------------------------------------------------------
| Id  | Operation         | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |               |       |       |    31 (100)|          |

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
|*  1 |  TABLE ACCESS FULL| TB_TABLE_LIST |     1 |    18 |    31   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      FULL(@"SEL$1" "T"@"SEL$1")
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - (rowset=256) "TABLE_NAME"[VARCHAR2,128]


已选择 43 行。

二、而后加入走索引的HINTS来更正这个SQL的执行计划，获得下面的执行计划相关信息，此时咱们就须要用这个执行计划来替换掉上面走全表扫描的SQL的执行计划。

SQL> SELECT /*+ INDEX(T IDX_TB_TABLE_LIST_TBNAME) */TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';


TABLE_NAME
------------------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
SQL_ID  44j1ysb93cwdq, child number 0
-------------------------------------
SELECT /*+ INDEX(T IDX_TB_TABLE_LIST_TBNAME) */TABLE_NAME FROM
TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$'

Plan hash value: 3318876060

---------------------------------------------------------------------------------------------
| Id  | Operation        | Name                     | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |                          |       |       |     1 (100)|          |

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
|*  1 |  INDEX RANGE SCAN| IDX_TB_TABLE_LIST_TBNAME |     1 |    18 |     1   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX(@"SEL$1" "T"@"SEL$1" ("TB_TABLE_LIST"."TABLE_NAME"))
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------

   1 - access("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - "TABLE_NAME"[VARCHAR2,128]


已选择 43 行。

三、下面查看对应的SQL_ID。

SQL> SELECT SQL_TEXT,SQL_ID FROM V$SQLAREA WHERE SQL_TEXT LIKE '%TABLE_NAME FROM TEST_ENV.TB_TABLE%';

SQL_TEXT                  SQL_ID
------------------------- -------------
SELECT /*+ INDEX(T IDX_TB 44j1ysb93cwdq
_TABLE_LIST_TBNAME) */TAB
LE_NAME FROM TEST_ENV.TB_
TABLE_LIST T WHERE TABLE_
NAME='ACCESS$'

SELECT SQL_TEXT,SQL_ID FR g4v1sg4ycf96y
OM V$SQLAREA WHERE SQL_TE
XT LIKE '%TABLE_NAME FROM
 TEST_ENV.TB_TABLE%'


SQL_TEXT                  SQL_ID
------------------------- -------------
SELECT /*+FULL(T)*/ TABLE 1a319c1c2b3rz
_NAME FROM TEST_ENV.TB_TA
BLE_LIST T WHERE TABLE_NA
ME='ACCESS$'

四、建立SQL PROFILE，用正确的执行计划的OUT LINE DATA来建立SQL Profile

SQL> declare
  2     v_hints sys.sqlprof_attr;
  3     clsql_text clob;
  4  begin
  5     v_hints := sys.sqlprof_attr('BEGIN_OUTLINE_DATA',
  6        'IGNORE_OPTIM_EMBEDDED_HINTS',
  7        'OPTIMIZER_FEATURES_ENABLE(''18.1.0'')',
  8        'DB_VERSION(''18.1.0'')',
  9        'ALL_ROWS',
 10        'OUTLINE_LEAF(@"SEL$1")',
 11        'INDEX(@"SEL$1" "T"@"SEL$1" ("TB_TABLE_LIST"."TABLE_NAME"))',
 12        'END_OUTLINE_DATA');
 13
 14      select sql_fulltext into clsql_text from v$sqlarea where sql_id='1a319c1c2b3rz';
 15
 16      dbms_sqltune.import_sql_profile(clsql_text,v_hints,'my_sql_profile',force_match=>true,replace=>true);
 17  end;
 18  /

PL/SQL 过程已成功完成。

五、最后再来看加FULL这个HINTS的SQL语句的执行计划，能够看到此时已是作的索引范围扫描了。

SQL> SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
------------------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
SQL_ID  1a319c1c2b3rz, child number 0
-------------------------------------
SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 3318876060

---------------------------------------------------------------------------------------------
| Id  | Operation        | Name                     | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |                          |       |       |     1 (100)|          |

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
|*  1 |  INDEX RANGE SCAN| IDX_TB_TABLE_LIST_TBNAME |     1 |    18 |     1   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX(@"SEL$1" "T"@"SEL$1" ("TB_TABLE_LIST"."TABLE_NAME"))
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------

   1 - access("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - "TABLE_NAME"[VARCHAR2,128]

Note

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
-----
   - SQL profile my_sql_profile used for this statement


已选择 47 行。

SPM

 SQL Plan Management(SPM)能够有效避免执行计划变动而致使的性能降低的问题，只有被验证和接受的执行计划才是可用的。SPM采用了一种叫SQL PLAN BASELINE的机制，它是一系列被验证性能良好的SQL执行计划的集合。无论SQL Plan Baseline仍是SQL Profile都是经过内部使用hints来实现的，他们之间的区别以下：

  1. SQL Plan BaseLine是一种偏主动的机制，能够在性能问题出现以前就建立SQL基线，避免优化器在将来某个时刻选择次优的执行计划。而SQL Profile只能等到发现SQL的性能问题时，调用SQL Tuning Advisor来对有问题的SQL进行调整。
  2. SQL Plan Baseline会重新产生一个具体的执行计划，不会随着其余相关统计信息的变动而变动，可是SQL Profile只是为优化器提供一个辅助信息。 SQL Plan Baseline的hints会指定生成一个具体的执行计划，可是SQL Profile的hints只是帮助调整优化器错误的计算

初始化参数配置

 能够经过如下两个参数来控制SPM的行为:

  • OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=TRUE|FALSE 该参数用于控制是否启用自动捕获SQL Plan Baseline，默认值为FALSE。该参数能够在SESSION或者SYSTEM级别进行修改，修改成TRUE后，ORACLE会对其影响的范围内的全部重复执行的SQL自动捕获其SQL Plan Baseline。对于第一次捕获到的结果，其ENABLED和ACCEPTED的值均为'YES'。当执行计划变动，被再次捕获到时，其ENABLED=YES可是ACCEPTED的值为'NO'，表示该SQL依然会使用第一次捕获到的SQL执行计划。
  • OPTIMIZER_USE_SQL_PLAN_BASELINES=TRUE|FALSE 该参数用于控制是否启用SQL Plan Baseline，默认值为TRUE，该参数也能够在SESSION和SYSTEM级别设置。

查看SQL Plan Baseline中的执行计划

 经过数据字典DBA_SQL_PLAN_BASELINES能够查询到存储在数据库中的SQL Plan Baselines，而后使用DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE函数能够查看对应的执行计划。

SELECT SIGNATURE,SQL_TEXT,SQL_HANDLE,PLAN_NAME FROM DBA_SQL_PLAN_BASELINES;

SELECT * from table(DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE('SQL_787830cec4402bdf','SQL_PLAN_7hy1htv240ayz01f095c0','advanced'));

批量加载SQL Plan Baseline

 经过DBMS_SPM包提供的相关函数，咱们能够从SQL Tuning Set、 Shared SQL Area和Staging Table中加载SQL Plan Baseline。比较经常使用的是经过Staging Table的方式来进行不一样数据库之间SQL Plan Baseline的迁移，好比咱们在测试库中调试好了一批SQL，须要将其执行计划导入到生产库中。  下面是经过Staging Table方式将A库的SQL Plan Baseline迁移到B库的基本流程：

  1. 使用DBMS_SPM.CREATE_STGTAB_BASELINE建立中间表。
BEGIN
  DBMS_SPM.CREATE_STGTAB_BASELINE (
    table_name => 'stage1');
END;
/
  1. 将SQL Plan Baseline打包到刚刚建立的中间表stage1
DECLARE
  v_plan_cnt NUMBER;
BEGIN
  v_plan_cnt := DBMS_SPM.PACK_STGTAB_BASELINE (
    table_name => 'stage1'
,   enabled    => 'yes'
,   creator    => 'spm'
);
END;
/
  1. 将中间表传输到目标数据库中，能够经过数据泵等手段。
  2. 在目标库中，将中间表的数据解压。
DECLARE
  v_plan_cnt NUMBER;
BEGIN
  v_plan_cnt := DBMS_SPM.UNPACK_STGTAB_BASELINE (
    table_name => 'stage1'
,   fixed      => 'yes'
);
END;
/

删除SQL Plan Baseline

 经过DBMS_SPM.DROP_SQL_PLAN_BASELINE函数能够删除已经保存的SQL Plan Baseline：

  1. 首先经过DBA_SQL_PLAN_BASELINES获取到对应的SQL_HANDLE
  2. 执行删除操做
SQL> EXEC DBMS_SPM.DROP_SQL_PLAN_BASELINE (sql_handle => 'SQL_b6b0d1c71cd1807b');

实例1——自动捕获

  1. 修改optimizer_capture_sql_plan_baselines参数启用自动捕获
SQL> alter system flush shared_pool;

系统已更改。

SQL> alter system flush buffer_cache;

系统已更改。

SQL> show parameter sql_plan

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     FALSE
optimizer_use_sql_plan_baselines     boolean     TRUE
SQL> alter system set optimizer_capture_sql_plan_baselines=TRUE;

系统已更改。

SQL> show parameter sql_pla

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     TRUE
optimizer_use_sql_plan_baselines     boolean     TRUE
  1. 第一次执行SQL，能够看到在DBA_SQL_PLAN_BASELINES中并未查到相应的SQL基线，再次执行才能查询到。
SQL> SET PAGES 10000 LINES 140
SQL> SET SERVEROUTPUT ON
SQL> COL SQL_TEXT FOR A20
SQL> COL SQL_HANDLE FOR A20
SQL> COL PLAN_NAME FOR A30
SQL> COL ORIGIN FOR A12
SQL> COL TABLE_NAME FOR A20
SQL> SET LONGC 60535
SQL> SET LONG 60535
SQL> SET ECHO ON
SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED, FIXED, AUTOPURGE FROM   DBA_SQL_PLAN_BASELINES W
HERE  SQL_TEXT LIKE '%TEST_ENV.TB_TABLE_LIST%';

未选定行
  1. 再次执行上面的SQL。查询DBA_SQL_PLAN_BASELINES，对应的SQL Plan Baseline的ACCEPTED和ENABLE的值均为YES。
SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED, FIXED, AUTOPURGE FROM   DBA_SQL_PLAN_BASELINES W
HERE  SQL_TEXT LIKE '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC FIX AUT
-------------------- -------------------- ------------------------------ ------------ --- --- --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 AUTO-CAPTURE YES YES NO  YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'
  1. 在表上建立一个TABLE_NAME列的B-TREE索引，而后再次执行上面的SQL语句，经过DBA_SQL_PLAN_BASELINES查询，此时多了一条SQL Plan Baseline，ENABLE=YES，ACCEPTED=NO
SQL> CREATE INDEX test_env.IDX_TB_TABLE_LIST_TBNAME ON TEST_ENV.TB_TABLE_LIST(TABLE_NAME);

索引已建立。

SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS('TEST_ENV','TB_TABLE_LIST',CASCADE=>TRUE);

PL/SQL 过程已成功完成。

SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED, FIXED, AUTOPURGE FROM   DBA_SQL_PLAN_BASELINES W
HERE  SQL_TEXT LIKE '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC FIX AUT
-------------------- -------------------- ------------------------------ ------------ --- --- --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES NO  NO  YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 AUTO-CAPTURE YES YES NO  YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'
  1. 在TABLE_NAME列建立索引以后，根据此列查询，应该是走INDEX RANGE SCAN，可是事实是怎么样呢？看下该语句的执行计划。
SQL> explain plan for SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

已解释。

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(null, null, 'basic +note'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------
--------------------
Plan hash value: 1475094007

-------------------------------------------
| Id  | Operation         | Name          |
-------------------------------------------
|   0 | SELECT STATEMENT  |               |
|   1 |  TABLE ACCESS FULL| TB_TABLE_LIST |
-------------------------------------------

Note
-----
   - SQL plan baseline "SQL_PLAN_7hy1htv240ayzc127edb7" used for this statement

已选择 12 行。

 能够看到，执行这个SQL依然走的是全表扫描，注意note部分，表示这个执行计划使用了"SQL_PLAN_7hy1htv240ayzc127edb7"的SQL Plan Baseline。代表了SPM能够很好的固定特定SQL的执行计划。 6. 可是实际上此时应该是走索引范围扫描才是最高效的，即"SQL_PLAN_7hy1htv240ayz01f095c0"这个SQL Plan Baseline，如何启用改baseline呢？首先建立一个evole任务，并执行该任务。

SQL> var cnt NUMBER
SQL> var tk_name VARCHAR2(50)
SQL> var exe_name VARCHAR2(50)
SQL> var evol_out CLOB
SQL> EXEC :tk_name := DBMS_SPM.CREATE_EVOLVE_TASK(sql_handle => 'SQL_787830cec4402bdf', plan_name  => 'SQL_PLAN_7hy1htv2
40ayz01f095c0');

PL/SQL 过程已成功完成。

SQL> print :tk_name

TK_NAME
--------
任务_31

SQL> EXEC :exe_name :=DBMS_SPM.EXECUTE_EVOLVE_TASK(task_name=>:tk_name);

PL/SQL 过程已成功完成。

SQL> print :exe_name

EXE_NAME
--------
EXEC_151
  1. 执行完成以后，经过REPORT_EVOLVE_TASK能够查看到相应的任务报告。Findings部分告诉咱们发现了一个比基线效率更高的执行计划，并提供了建议方案。
SQL> EXEC :evol_out := DBMS_SPM.REPORT_EVOLVE_TASK( task_name=>:tk_name, execution_name=>:exe_name );

PL/SQL 过程已成功完成。

SQL> SELECT :evol_out FROM DUAL;

:EVOL_OUT
------------------------------------------------------------------------------------------------------------------------
--------------------
GENERAL INFORMATION SECTION
---------------------------------------------------------------------------------------------

 Task Information:
 ---------------------------------------------
 Task Name            : 任务_31
 Task Owner           : SYS
 Execution Name       : EXEC_151
 Execution Type       : SPM EVOLVE
 Scope                : COMPREHENSIVE
 Status               : COMPLETED
 Started              : 04/19/2019 16:45:33
 Finished             : 04/19/2019 16:45:33
 Last Updated         : 04/19/2019 16:45:33
 Global Time Limit    : 2147483646
 Per-Plan Time Limit  : UNUSED
 Number of Errors     : 0
---------------------------------------------------------------------------------------------

SUMMARY SECTION
---------------------------------------------------------------------------------------------
  Number of plans processed  : 1
  Number of findings         : 1
  Number of recommendations  : 1
  Number of errors           : 0
---------------------------------------------------------------------------------------------

DETAILS SECTION
---------------------------------------------------------------------------------------------
 Object ID          : 2
 Test Plan Name     : SQL_PLAN_7hy1htv240ayz01f095c0
 Base Plan Name     : SQL_PLAN_7hy1htv240ayzc127edb7
 SQL Handle         : SQL_787830cec4402bdf
 Parsing Schema     : SYS
 Test Plan Creator  : SYS
 SQL Text           : SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
                    TABLE_NAME='ACCESS$'

Execution Statistics:
-----------------------------
                    Base Plan                     Test Plan
                    ----------------------------  ----------------------------
 Elapsed Time (s):  .000016                       .000001
 CPU Time (s):      0                             0
 Buffer Gets:       10                            0
 Optimizer Cost:    31                            1
 Disk Reads:        0                             0
 Direct Writes:     0                             0
 Rows Processed:    0                             0
 Executions:        10                            10


FINDINGS SECTION
---------------------------------------------------------------------------------------------

Findings (1):
-----------------------------
 1. 计划已在 0.03200 秒内验证完毕。此计划符合收益标准, 这是由于其验证性能比基线计划的性能高 50.50000 倍。

Recommendation:
-----------------------------
 Consider accepting the plan. Execute
 dbms_spm.accept_sql_plan_baseline(task_name => '任务_31', object_id => 2,
 task_owner => 'SYS');


EXPLAIN PLANS SECTION
---------------------------------------------------------------------------------------------

Baseline Plan
-----------------------------
 Plan Id          : 201
 Plan Hash Value  : 3240619447

------------------------------------------------------------------------------
| Id  | Operation           | Name          | Rows | Bytes | Cost | Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |               |    1 |    18 |   31 | 00:00:01 |
| * 1 |   TABLE ACCESS FULL | TB_TABLE_LIST |    1 |    18 |   31 | 00:00:01 |
------------------------------------------------------------------------------

Predicate Information (identified by operation id):
------------------------------------------
* 1 - filter("TABLE_NAME"='ACCESS$')


Test Plan
-----------------------------
 Plan Id          : 202
 Plan Hash Value  : 32544192

----------------------------------------------------------------------------------------
| Id  | Operation          | Name                     | Rows | Bytes | Cost | Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |                          |    1 |    18 |    1 | 00:00:01 |
| * 1 |   INDEX RANGE SCAN | IDX_TB_TABLE_LIST_TBNAME |    1 |    18 |    1 | 00:00:01 |
----------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
------------------------------------------
* 1 - access("TABLE_NAME"='ACCESS$')

---------------------------------------------------------------------------------------------
  1. 能够经过上面报告中建议的方式来接受这个计划，也可使用IMPLEMENT_EVOLVE_TASK函数。
SQL> EXEC :cnt := DBMS_SPM.IMPLEMENT_EVOLVE_TASK( task_name=>:tk_name, execution_name=>:exe_name );

PL/SQL 过程已成功完成。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE  SQL_HANDLE='
SQL_787830cec4402bdf';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 AUTO-CAPTURE YES YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'
  1. 最后咱们再来看下执行计划
SQL> explain plan for SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

已解释。

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(null, null, 'basic +note'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3318876060

-----------------------------------------------------
| Id  | Operation        | Name                     |
-----------------------------------------------------
|   0 | SELECT STATEMENT |                          |
|   1 |  INDEX RANGE SCAN| IDX_TB_TABLE_LIST_TBNAME |
-----------------------------------------------------

Note
-----
   - SQL plan baseline "SQL_PLAN_7hy1htv240ayz01f095c0" used for this statement

已选择 12 行。

 能够看到此时已经走了索引范围扫描，使用的是"SQL_PLAN_7hy1htv240ayz01f095c0"这个SQL Plan Baseline。当存在多个计划的ACCEPTED和ENABLE的值都为YES的时候，优化器会选择一个成本更低的计划来执行。

实例2——手工生成

 接下来看下手工生成SQL Plan Baseline的方法。其实很是简单，核心就是经过DBMS_STATS.LOAD_PLANS_FROM_CURSOR_CACHE来从Shared SQL Area中加载执行计划。

  1. 首先对前面例子生成的内容进行清理。
SQL> alter system set optimizer_capture_sql_plan_baselines=false;

系统已更改。

SQL> show parameter sql_pla

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
optimizer_capture_sql_plan_baselines boolean     FALSE
optimizer_use_sql_plan_baselines     boolean     TRUE

SQL> EXEC :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE('SQL_787830cec4402bdf');

PL/SQL 过程已成功完成。

SQL> EXEC :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE('SQL_061becb140fad607');

PL/SQL 过程已成功完成。

SQL> EXEC :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE('SQL_ecca2815c7166fb6');

PL/SQL 过程已成功完成。

SQL> EXEC :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE('SQL_9049245213a986b3');

PL/SQL 过程已成功完成。

SQL> EXEC :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE('SQL_85372e07e425b213');

PL/SQL 过程已成功完成。

SQL> DELETE FROM SQLLOG$;

已删除 9 行。

SQL> commit;

提交完成。

SQL> alter system flush shared_pool;

系统已更改。

SQL> alter system flush buffer_cache;

系统已更改。
  1. 执行SQL并查看执行计划
SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

SQL_ID  drmkgq2ppg7kg, child number 0
-------------------------------------
SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 1475094007

-----------------------------------------------------------------------------------
| Id  | Operation         | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |               |       |       |    31 (100)|          |

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

|*  1 |  TABLE ACCESS FULL| TB_TABLE_LIST |     1 |    18 |    31   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      FULL(@"SEL$1" "T"@"SEL$1")
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - (rowset=256) "TABLE_NAME"[VARCHAR2,128]


已选择 43 行。
  1. 由于此时自动捕获是关闭的，因此无论执行多少次SQL，都没有对应的SQL Plan Baseline。能够手动的将对应的执行计划加入到SQL Plan Baseline中。
SQL> var cnt number
SQL> exec :cnt := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE(sql_id=>'drmkgq2ppg7kg', plan_hash_value=>'1475094007');

PL/SQL 过程已成功完成。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES
                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-
                     _LIST T WHERE TABLE_                                CACHE
                     NAME='ACCESS$'
  1. 在TABLE_NAME列上建立索引，而后再次执行SQL，并查看执行计划。能够看到虽然在TABLE_NAME这个列上存在索引，可是已经存在对应SQL语句的一个走全表扫描的执行基线，因此此时依旧走的全表扫描，使用的是刚刚加载进去的'SQL_PLAN_7hy1htv240ayzc127edb7'这个SQL Plan Baseline。
SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------

SQL_ID  drmkgq2ppg7kg, child number 1
-------------------------------------
SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 1475094007

-----------------------------------------------------------------------------------
| Id  | Operation         | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |               |       |       |    31 (100)|          |

PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------

|*  1 |  TABLE ACCESS FULL| TB_TABLE_LIST |     1 |    18 |    31   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      FULL(@"SEL$1" "T"@"SEL$1")
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - (rowset=256) "TABLE_NAME"[VARCHAR2,128]

Note

PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------

-----
   - SQL plan baseline SQL_PLAN_7hy1htv240ayzc127edb7 used for this statement


已选择 47 行。
  1. 这个时候咱们再来查看下DBA_SQL_PLAN_BASELINES这个数据字典，能够看到SPM帮咱们自动捕获了一条ENABLE为YES，ACCEPTED为NO的SQL Plan Baseline。
SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE
 '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES NO
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES
                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-
                     _LIST T WHERE TABLE_                                CACHE
                     NAME='ACCESS$'
  1. 将'SQL_PLAN_7hy1htv240ayz01f095c0'的ACCEPTED的值改成YES。
SQL> var result clob;
SQL> EXEC :result :=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_787830cec4402bdf', PLAN_NAME=>'SQL_PLAN_7hy1htv24
0ayz01f095c0', VERIFY=>'NO', COMMIT=>'YES');

PL/SQL 过程已成功完成。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE
 '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES
                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-
                     _LIST T WHERE TABLE_                                CACHE
                     NAME='ACCESS$'
  1. 再次执行SQL，此时使用了'SQL_PLAN_7hy1htv240ayz01f095c0'这个SQL Plan Baseline了。
SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

SQL_ID  drmkgq2ppg7kg, child number 0
-------------------------------------
SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 3318876060

---------------------------------------------------------------------------------------------
| Id  | Operation        | Name                     | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |                          |       |       |     1 (100)|          |

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

|*  1 |  INDEX RANGE SCAN| IDX_TB_TABLE_LIST_TBNAME |     1 |    18 |     1   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX(@"SEL$1" "T"@"SEL$1" ("TB_TABLE_LIST"."TABLE_NAME"))
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - access("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - "TABLE_NAME"[VARCHAR2,128]

Note

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

-----
   - SQL plan baseline SQL_PLAN_7hy1htv240ayz01f095c0 used for this statement


已选择 47 行。
  1. 前面的SQL都是没有HINTS的，有时候咱们需加入HINTS对SQL的执行计划进行调整。如何用加入了hints的SQL执行计划来替换以前的SQL，生成新的SQL Plan Baseline呢？首先删除以前作全表扫描的SQL Plan Baseline，而后加入一个FULL的hints来执行SQL，此时SQL_ID和以前是不一样的。
SQL> exec :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE (sql_handle=>'SQL_787830cec4402bdf', plan_name=>'SQL_PLAN_7hy1htv240ayz
c127edb7');

PL/SQL 过程已成功完成。

SQL> SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------

SQL_ID  1a319c1c2b3rz, child number 0
-------------------------------------
SELECT /*+FULL(T)*/ TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 1475094007

-----------------------------------------------------------------------------------
| Id  | Operation         | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |               |       |       |    31 (100)|          |

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------

|*  1 |  TABLE ACCESS FULL| TB_TABLE_LIST |     1 |    18 |    31   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      FULL(@"SEL$1" "T"@"SEL$1")
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - (rowset=256) "TABLE_NAME"[VARCHAR2,128]


已选择 43 行。

 此时从索引范围扫描变成了全表扫描，SQL_ID为1a319c1c2b3rz，PLAN_HASH_VALUE为1475094007 9. 此时的DBA_SQL_PLAN_BASELINES依然以后刚刚那一条记录。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE
 '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'
  1. 如今用上述改写后的SQL的新的执行计划来手工生成SQL Plan Baseline
SQL> exec :cnt := dbms_spm.load_plans_from_cursor_cache(sql_id => '1a319c1c2b3rz', plan_hash_value=>1475094007, sql_handle=>'SQL_787830cec4402bdf')

PL/SQL 过程已成功完成。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE
 '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE YES YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES
                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-
                     _LIST T WHERE TABLE_                                CACHE
                     NAME='ACCESS$'
  1. 因为此时所对应的SQL Plan Baseline的ENABLED和ACCEPTED的值都为YES，咱们将以前的走索引范围扫描的ENABLED属性改成NO，而后执行SQL语句。
SQL> EXEC :CNT := DBMS_SPM.ALTER_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_787830cec4402bdf', PLAN_NAME=>'SQL_PLAN_7hy1htv240ay
z01f095c0', ATTRIBUTE_NAME=>'ENABLED', ATTRIBUTE_VALUE=>'NO');

PL/SQL 过程已成功完成。

SQL> SELECT SQL_HANDLE, SQL_TEXT, PLAN_NAME, ORIGIN, ENABLED, ACCEPTED FROM   DBA_SQL_PLAN_BASELINES WHERE SQL_TEXT LIKE
 '%TEST_ENV.TB_TABLE_LIST%';

SQL_HANDLE           SQL_TEXT             PLAN_NAME                      ORIGIN       ENA ACC
-------------------- -------------------- ------------------------------ ------------ --- ---
SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayz01f095c0 AUTO-CAPTURE NO  YES
                     OM TEST_ENV.TB_TABLE
                     _LIST T WHERE TABLE_
                     NAME='ACCESS$'

SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES
                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-
                     _LIST T WHERE TABLE_                                CACHE
                     NAME='ACCESS$'

SQL> SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$';

TABLE_NAME
--------------------
ACCESS$

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(NULL, NULL, 'advanced'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

SQL_ID  drmkgq2ppg7kg, child number 1
-------------------------------------
SELECT TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE
TABLE_NAME='ACCESS$'

Plan hash value: 1475094007

-----------------------------------------------------------------------------------
| Id  | Operation         | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |               |       |       |    31 (100)|          |

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

|*  1 |  TABLE ACCESS FULL| TB_TABLE_LIST |     1 |    18 |    31   (0)| 00:00:01 |
-----------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / T@SEL$1

Outline Data
-------------


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('18.1.0')
      DB_VERSION('18.1.0')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      FULL(@"SEL$1" "T"@"SEL$1")
      END_OUTLINE_DATA
  */


PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("TABLE_NAME"='ACCESS$')

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - (rowset=256) "TABLE_NAME"[VARCHAR2,128]

Note

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------

-----
   - SQL plan baseline SQL_PLAN_7hy1htv240ayzc127edb7 used for this statement


已选择 47 行。

 能够看到此时的执行计划就是刚刚加HINTS的SQL语句的执行计划了。

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