oracle spm使用1

Posted 2020-09-18 jhcelue

oracle11g new feature SPM
有助于保持sql的语句特性，仅仅同意运行性能提高的运行计划。
它不同于stored outlines， spm在于稳定sql性能，而store outlines在于冻结sql运行计划


事列
1.启用optimizer_cature_sql_plan_baselines 捕获sql语句
SQL> alter session set optimizer_capture_sql_plan_baselines = true;
Session altered.
SQL> select * from objs where object_id = 2;
no rows selected
SQL> select * from objs where object_id = 2;
no rows selected
SQL> alter session set optimizer_capture_sql_plan_baselines = false;
Session altered.
2.查询dba_sql_plan_baselines，确定sql的spm状态
SQL> select plan_name, sql_handle, enabled, accepted, fixed,
  2             module, sql_text
  3  from dba_sql_plan_baselines;
PLAN_NAME                      SQL_HANDLE           ENABLED   ACCEPTED  FIXED     MODULE               SQL_TEXT
------------------------------ -------------------- --------- --------- --------- -------------------- --------------------------------------------------
SQL_PLAN_4pzq3z6xcqkpwd0984253 SQL_4afec3f9bacb4abc YES       YES       NO        SQL*Plus             select * from objs where object_id = 2
3.添加索引改变环境再执行sql
SQL> alter session set optimizer_capture_sql_plan_baselines = true;
Session altered.
SQL> select * from objs where object_id = 2;
no rows selected
SQL> select * from objs where object_id = 2;
no rows selected
SQL> alter session set optimizer_capture_sql_plan_baselines = false;
Session altered.
4.查询dba_sql_plan_baselines
SQL> select plan_name, sql_handle, enabled, accepted, fixed, module, sql_text from dba_sql_plan_baselines;
PLAN_NAME                      SQL_HANDLE           ENABLED   ACCEPTED  FIXED     MODULE               SQL_TEXT
------------------------------ -------------------- --------- --------- --------- -------------------- --------------------------------------------------
SQL_PLAN_4pzq3z6xcqkpwbe4c314c SQL_4afec3f9bacb4abc YES       NO        NO        SQL*Plus             select * from objs where object_id = 2
SQL_PLAN_4pzq3z6xcqkpwd0984253 SQL_4afec3f9bacb4abc YES       YES       NO        SQL*Plus             select * from objs where object_id = 2
SQL>
5.測试
SQL>
SQL> set autotrace on
SQL> select * from objs where object_id = 2;
no rows selected
Execution Plan
----------------------------------------------------------
Plan hash value: 954894094


--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |    98 |   247   (1)| 00:00:03 |
|*  1 |  TABLE ACCESS FULL| OBJS |     1 |    98 |   247   (1)| 00:00:03 |
--------------------------------------------------------------------------


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


   1 - filter("OBJECT_ID"=2)


Note
-----
   - SQL plan baseline "SQL_PLAN_4pzq3z6xcqkpwd0984253" used for this statement




Statistics
----------------------------------------------------------
        255  recursive calls
          0  db block gets
       1044  consistent gets
        879  physical reads
          0  redo size
       1343  bytes sent via SQL*Net to client
        513  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
         28  sorts (memory)
          0  sorts (disk)
          0  rows processed


SQL> alter session set optimizer_use_sql_plan_baselines = false;
Session altered.
SQL> select * from objs where object_id = 2;
no rows selected
Execution Plan
----------------------------------------------------------
Plan hash value: 613004408


-----------------------------------------------------------------------------------------------
| Id  | Operation                   | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                 |     1 |    98 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| OBJS            |     1 |    98 |     2   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | IDX_OBJSID_OBJS |     1 |       |     1   (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------


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


   2 - access("OBJECT_ID"=2)




Statistics
----------------------------------------------------------
          1  recursive calls
          0  db block gets
          2  consistent gets
          4  physical reads
          0  redo size
       1343  bytes sent via SQL*Net to client
        513  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          0  rows processed

能够看到当启动optimizer_user_sql_plan_baselines时走索引应该是最优的却没有使用
plan_name accecpt 为 no 影响了走索引计划