稳定ORACLE的执行计划-秋月博客

原文发表在:http://l4j.cc/2019/04/19/oracle-sql-plan-management/ 很多时候可能我们都希望CBO能够帮我们生成正确、高效的执行计划，但是很多时候事实并

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

很多时候可能我们都希望CBO能够帮我们生成正确、高效的执行计划，但是很多时候事实并非如此，可能因为各种各样的原因(如，统计信息不正确或者CBO天生的缺陷等)都会导致生成的执行计划特别的低效。之前的一家公司有一台专门用于批量做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，统计信息经常会发生较大的变更，之前跑得好好的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导致了执行计划的变更。

这时候我们就希望数据库中运行的SQL都能有正确、稳定的执行计划，在10g开始的版本中可以通过SQL Profile来稳定执行计划或者在不改变SQL的情况下修改执行计划。11g开始可以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。

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，可以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以下信息：

SQL Profile提供的辅助统计信息
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。

所以，上面两个条件的任意一个发生变化，都有可能导致执行计划的改变。下面看下SQL Profile的一些基本操作以及如何在线进行SQL的调整。

accepting sql profile

通过DBMS_SQLTUNE.ACCEPT_SQL_PROFILE存储过程可以接受一个SQL Profile，只有在我们接受了一个SQL Profile之后，优化器才能使用他作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：

profile_type这个参数用于控制是否改变并行执行行为，REGULAR_PROFILE 不更改为并行执行，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，所以当字面值不同时也可以重用该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：

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

可以通过DBA_SQL_PROFILES数据字典视图来查看存储在数据库中的SQL Profile。

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

通过ALTER_SQL_PROFILE中的attribute_name参数可以修改SQL Profile相应的参数值。

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

Droping SQL Profile

通过DROP_SQL_PROFILE存储过程可以删除特定的SQL Profile

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

通过SQL Profile调整线上SQL执行计划

通过手工创建SQL Profile的方式，可以在不更改目标SQL的SQL文本的情况下修改SQL的执行计划，而且可以很好的稳定SQL的执行计划。下面是手工创建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：1、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 WHERETABLE_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$1Outline 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。

2、然后加入走索引的HINTS来更正这个SQL的执行计划，得到下面的执行计划相关信息，此时我们就需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 FROMTEST_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$1Outline 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。

3、下面查看对应的SQL_ID。

SQL> SELECT SQL_TEXT,SQL_ID FROM V$SQLAREA WHERE SQL_TEXT LIKE '%TABLE_NAME FROM TEST_ENV.TB_TABLE%';SQL_TEXT                  SQL_ID------------------------- -------------SELECT /*+ INDEX(T IDX_TB 44j1ysb93cwdq_TABLE_LIST_TBNAME) */TABLE_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$'SELECT SQL_TEXT,SQL_ID FR g4v1sg4ycf96yOM V$SQLAREA WHERE SQL_TEXT LIKE '%TABLE_NAME FROM TEST_ENV.TB_TABLE%'SQL_TEXT                  SQL_ID------------------------- -------------SELECT /*+FULL(T)*/ TABLE 1a319c1c2b3rz_NAME FROM TEST_ENV.TB_TABLE_LIST T WHERE TABLE_NAME='ACCESS$'

4、创建SQL PROFILE，用正确的执行计划的OUT LINE DATA来创建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。

5、最后再来看加FULL这个HINTS的SQL语句的执行计划，可以看到此时已经是做的索引范围扫描了。

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 WHERETABLE_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$1Outline 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]NotePLAN_TABLE_OUTPUT---------------------------------------------------------------------------------------------------------   - SQL profile my_sql_profile used for this statement已选择 47 行。

SPM

SQL Plan Management(SPM)可以有效避免执行计划变更而导致的性能下降的问题，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 PLANBASELINE的机制，它是一系列被验证性能良好的SQL执行计划的集合。不管SQL Plan Baseline还是SQL Profile都是通过内部使用hints来实现的，他们之间的区别如下：

SQL Plan BaseLine是一种偏主动的机制，可以在性能问题出现之前就创建SQL基线，避免优化器在未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。
SQL Plan Baseline会从新产生一个具体的执行计划，不会随着其他相关统计信息的变更而变更，但是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，但是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

可以通过以下两个参数来控制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。该参数可以在SESSION或者SYSTEM级别进行修改，修改为TRUE后，ORACLE会对其影响的范围内的所有重复执行的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'。当执行计划变更，被再次捕获到时，其ENABLED=YES但是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，该参数也可以在SESSION和SYSTEM级别设置。

查看SQL Plan Baseline中的执行计划

通过数据字典DBA_SQL_PLAN_BASELINES可以查询到存储在数据库中的SQL Plan Baselines，然后使用DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE函数可以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

通过DBMS_SPM包提供的相关函数，我们可以从SQL Tuning Set、 Shared SQL Area和Staging Table中加载SQL Plan Baseline。比较常用的是通过Staging Table的方式来进行不同数据库之间SQL Plan Baseline的迁移，比如我们在测试库中调试好了一批SQL，需要将其执行计划导入到生产库中。下面是通过Staging Table方式将A库的SQL Plan Baseline迁移到B库的基本流程：

使用DBMS_SPM.CREATE_STGTAB_BASELINE创建中间表。

BEGIN  DBMS_SPM.CREATE_STGTAB_BASELINE (    table_name => 'stage1');END;/

将SQL Plan Baseline打包到刚刚创建的中间表stage1

DECLARE  v_plan_cnt NUMBER;BEGIN  v_plan_cnt := DBMS_SPM.PACK_STGTAB_BASELINE (    table_name => 'stage1',   enabled    => 'yes',   creator    => 'spm');END;/

将中间表传输到目标数据库中，可以通过数据泵等手段。
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

通过DBMS_SPM.DROP_SQL_PLAN_BASELINE函数可以删除已经保存的SQL Plan Baseline：

首先通过DBA_SQL_PLAN_BASELINES获取到对应的SQL_HANDLE
执行删除操作

SQL> EXEC DBMS_SPM.DROP_SQL_PLAN_BASELINE (sql_handle => 'SQL_b6b0d1c71cd1807b');

实例1——自动捕获

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_planNAME                                 TYPE        VALUE------------------------------------ ----------- ------------------------------optimizer_capture_sql_plan_baselines boolean     FALSEoptimizer_use_sql_plan_baselines     boolean     TRUESQL> alter system set optimizer_capture_sql_plan_baselines=TRUE;系统已更改。SQL> show parameter sql_plaNAME                                 TYPE        VALUE------------------------------------ ----------- ------------------------------optimizer_capture_sql_plan_baselines boolean     TRUEoptimizer_use_sql_plan_baselines     boolean     TRUE

第一次执行SQL，可以看到在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 140SQL> SET SERVEROUTPUT ONSQL> COL SQL_TEXT FOR A20SQL> COL SQL_HANDLE FOR A20SQL> COL PLAN_NAME FOR A30SQL> COL ORIGIN FOR A12SQL> COL TABLE_NAME FOR A20SQL> SET LONGC 60535SQL> SET LONG 60535SQL> SET ECHO ONSQL> 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 WHERE  SQL_TEXT LIKE '%TEST_ENV.TB_TABLE_LIST%';未选定行

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 WHERE  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$'

在表上创建一个TABLE_NAME列的B-TREE索引，然后再次执行上面的SQL语句，通过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);索引已创建。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 WHERE  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$'SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 AUTO-CAPTURE YES YES NO  YES                     OM TEST_ENV.TB_TABLE                     _LIST T WHERE TABLE_                     NAME='ACCESS$'

在TABLE_NAME列创建索引之后，根据此列查询，应该是走INDEX RANGE SCAN，但是事实是怎么样呢？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。

可以看到，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。表明了SPM可以很好的固定特定SQL的执行计划。6. 但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？首先创建一个evole任务，并执行该任务。

SQL> var cnt NUMBERSQL> var tk_name VARCHAR2(50)SQL> var exe_name VARCHAR2(50)SQL> var evol_out CLOBSQL> EXEC :tk_name := DBMS_SPM.CREATE_EVOLVE_TASK(sql_handle => 'SQL_787830cec4402bdf', plan_name  => 'SQL_PLAN_7hy1htv240ayz01f095c0');PL/SQL 过程已成功完成。SQL> print :tk_nameTK_NAME--------任务_31SQL> EXEC :exe_name :=DBMS_SPM.EXECUTE_EVOLVE_TASK(task_name=>:tk_name);PL/SQL 过程已成功完成。SQL> print :exe_nameEXE_NAME--------EXEC_151

执行完成之后，通过REPORT_EVOLVE_TASK可以查看到相应的任务报告。Findings部分告诉我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$'Execution Statistics:-----------------------------                    Base Plan                     Test Plan                    ----------------------------  ---------------------------- Elapsed Time (s):  .000016                       .000001 CPU Time (s):      0                             0 Buffer Gets:       10                            0 Optimizer Cost:    31                            1 Disk Reads:        0                             0 Direct Writes:     0                             0 Rows Processed:    0                             0 Executions:        10                            10FINDINGS SECTION---------------------------------------------------------------------------------------------Findings (1):----------------------------- 1. 计划已在 0.03200 秒内验证完毕。此计划符合收益标准, 这是因为其验证性能比基线计划的性能高 50.50000 倍。Recommendation:----------------------------- Consider accepting the plan. Execute dbms_spm.accept_sql_plan_baseline(task_name => '任务_31', object_id => 2, task_owner => 'SYS');EXPLAIN PLANS SECTION---------------------------------------------------------------------------------------------Baseline Plan----------------------------- Plan Id          : 201 Plan Hash Value  : 3240619447------------------------------------------------------------------------------| Id  | Operation           | Name          | Rows | Bytes | Cost | Time     |------------------------------------------------------------------------------|   0 | SELECT STATEMENT    |               |    1 |    18 |   31 | 00:00:01 || * 1 |   TABLE ACCESS FULL | TB_TABLE_LIST |    1 |    18 |   31 | 00:00:01 |------------------------------------------------------------------------------Predicate Information (identified by operation id):------------------------------------------* 1 - filter("TABLE_NAME"='ACCESS$')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$')---------------------------------------------------------------------------------------------

可以通过上面报告中建议的方式来接受这个计划，也可以使用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$'SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 AUTO-CAPTURE YES YES                     OM TEST_ENV.TB_TABLE                     _LIST T WHERE TABLE_                     NAME='ACCESS$'

最后我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。

可以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。其实非常简单，核心就是通过DBMS_STATS.LOAD_PLANS_FROM_CURSOR_CACHE来从Shared SQL Area中加载执行计划。

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_plaNAME                                 TYPE        VALUE------------------------------------ ----------- ------------------------------optimizer_capture_sql_plan_baselines boolean     FALSEoptimizer_use_sql_plan_baselines     boolean     TRUESQL> 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。

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 WHERETABLE_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$1Outline 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。

因为此时自动捕获是关闭的，所以不管执行多少次SQL，都没有对应的SQL Plan Baseline。可以手动的将对应的执行计划加入到SQL Plan Baseline中。

SQL> var cnt numberSQL> 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$'

在TABLE_NAME列上创建索引，然后再次执行SQL，并查看执行计划。可以看到虽然在TABLE_NAME这个列上存在索引，但是已经存在对应SQL语句的一个走全表扫描的执行基线，所以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 WHERETABLE_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$1Outline 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]NotePLAN_TABLE_OUTPUT----------------------------------------------------------------------------------------------------------------------------   - SQL plan baseline SQL_PLAN_7hy1htv240ayzc127edb7 used for this statement已选择 47 行。

这个时候我们再来查看下DBA_SQL_PLAN_BASELINES这个数据字典，可以看到SPM帮我们自动捕获了一条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$'SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-                     _LIST T WHERE TABLE_                                CACHE                     NAME='ACCESS$'

将'SQL_PLAN_7hy1htv240ayz01f095c0'的ACCEPTED的值改为YES。

SQL> var result clob;SQL> EXEC :result :=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_787830cec4402bdf', PLAN_NAME=>'SQL_PLAN_7hy1htv240ayz01f095c0', 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$'SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-                     _LIST T WHERE TABLE_                                CACHE                     NAME='ACCESS$'

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 WHERETABLE_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$1Outline 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]NotePLAN_TABLE_OUTPUT-----------------------------------------------------------------------------------------------------------------------------   - SQL plan baseline SQL_PLAN_7hy1htv240ayz01f095c0 used for this statement已选择 47 行。

前面的SQL都是没有HINTS的，有时候我们需加入HINTS对SQL的执行计划进行调整。如何用加入了hints的SQL执行计划来替换之前的SQL，生成新的SQL Plan Baseline呢？首先删除之前做全表扫描的SQL Plan Baseline，然后加入一个FULL的hints来执行SQL，此时SQL_ID和之前是不同的。

SQL> exec :cnt :=DBMS_SPM.DROP_SQL_PLAN_BASELINE (sql_handle=>'SQL_787830cec4402bdf', plan_name=>'SQL_PLAN_7hy1htv240ayzc127edb7');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 WHERETABLE_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$1Outline 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14750940079. 此时的DBA_SQL_PLAN_BASELINES依然之后刚刚那一条记录。

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$'

现在用上述改写后的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$'SQL_787830cec4402bdf SELECT TABLE_NAME FR SQL_PLAN_7hy1htv240ayzc127edb7 MANUAL-LOAD- YES YES                     OM TEST_ENV.TB_TABLE                                FROM-CURSOR-                     _LIST T WHERE TABLE_                                CACHE                     NAME='ACCESS$'

由于此时所对应的SQL Plan Baseline的ENABLED和ACCEPTED的值都为YES，我们将之前的走索引范围扫描的ENABLED属性改为NO，然后执行SQL语句。

SQL> EXEC :CNT := DBMS_SPM.ALTER_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_787830cec4402bdf', PLAN_NAME=>'SQL_PLAN_7hy1htv240ayz01f095c0', 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 WHERETABLE_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$1Outline 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]NotePLAN_TABLE_OUTPUT-----------------------------------------------------------------------------------------------------------------------------   - SQL plan baseline SQL_PLAN_7hy1htv240ayzc127edb7 used for this statement已选择 47 行。

可以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。

目录CONTENT

稳定ORACLE的执行计划