spm手工创建sql_plan_baseline
本文参考崔华老师的书
1)创建一个测试表
create table t2 as select * from dba_objects;
create index idx_t2 on t2(object_id);
2)做一次查询
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4;
查一下执行计划
select * from table(dbms_xplan.display_cursor(null,null,'advanced'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 76td2qkxcrn9v, child number 0
-------------------------------------
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where
object_id=4
Plan hash value: 1513984157
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 345 (100)| |
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|* 1 | TABLE ACCESS FULL| T2 | 14 | 1106 | 345 (1)| 00:00:05 |
--------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
3)查看一下是否有sql_plan_baseline
select sql_handle,plan_name,origin,enabled,accepted,sql_text from dba_sql_plan_baselines where
sql_text like 'select /*+ no_index(t2 idx_t2) */object_name%';
no rows selected
我的环境
optimizer_capture_sql_plan_baselines boolean 参数值是FALSE
4)生成1个sql_plan_baseline
var temp number
exec :temp := dbms_spm.load_plans_from_cursor_cache(sql_id => '76td2qkxcrn9v',plan_hash_value=>1513984157);
5)再查询一下
select sql_handle,plan_name,origin,enabled,accepted,sql_text from dba_sql_plan_baselines where
sql_text like 'select /*+ no_index(t2 idx_t2) */object_name%';
有结果了
SQL_HANDLE PLAN_NAME ORIGIN ENA
------------------------------ ------------------------------ -------------- ---
ACC
---
SQL_TEXT
--------------------------------------------------------------------------------
SQL_75b06ae056223f5f SQL_PLAN_7bc3aw1b24guzb860bcf2 MANUAL-LOAD YES
YES
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4
6)改写原来的sql,强制走索引hint
select /*+ index(t2 idx_t2) */object_name,object_id from t2 where object_id=4;
select * from table(dbms_xplan.display_cursor(null,null,'advanced'));
SQL_ID 795jg57h9tryx, child number 0
-------------------------------------
select /*+ index(t2 idx_t2) */object_name,object_id from t2 where
object_id=4
Plan hash value: 2008370210
--------------------------------------------------------------------------------
------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|
--------------------------------------------------------------------------------
------
| 0 | SELECT STATEMENT | | | | 2 (100)|
|
| 1 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 79 | 2 (0)| 00:0
0:01 |
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|* 2 | INDEX RANGE SCAN | IDX_T2 | 1 | | 1 (0)| 00:0
0:01 |
--------------------------------------------------------------------------------
这个走索引明显效率高
7)再查询一下是否有新的sql_plan_baseline (应该没有的)
SQL> select sql_handle,plan_name,origin,enabled,accepted,sql_text from dba_sql_plan_baselines where
2 sql_text like 'select /*+ no_index(t2 idx_t2) */object_name%';
SQL_HANDLE PLAN_NAME ORIGIN ENA
------------------------------ ------------------------------ -------------- ---
ACC
---
SQL_TEXT
--------------------------------------------------------------------------------
SQL_75b06ae056223f5f SQL_PLAN_7bc3aw1b24guzb860bcf2 MANUAL-LOAD YES
YES
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4
8)偷梁换柱
exec :temp := dbms_spm.load_plans_from_cursor_cache(sql_id => '795jg57h9tryx',plan_hash_value=>2008370210,sql_handle =>'SQL_75b06ae056223f5f');
查询新的基线有两个了
SQL> select sql_handle,plan_name,origin,enabled,accepted,sql_text from dba_sql_plan_baselines where
2 sql_text like 'select /*+ no_index(t2 idx_t2) */object_name%';
SQL_HANDLE PLAN_NAME ORIGIN ENA
------------------------------ ------------------------------ -------------- ---
ACC
---
SQL_TEXT
--------------------------------------------------------------------------------
SQL_75b06ae056223f5f SQL_PLAN_7bc3aw1b24guz24c6dbb6 MANUAL-LOAD YES
YES
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4
SQL_75b06ae056223f5f SQL_PLAN_7bc3aw1b24guzb860bcf2 MANUAL-LOAD YES
YES
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4
9)删掉旧的一个
exec :temp := dbms_spm.drop_sql_plan_baseline(sql_handle =>'SQL_75b06ae056223f5f',plan_name=>'SQL_PLAN_7bc3aw1b24guzb860bcf2');
查看一下只剩下改写的一个
SQL> select sql_handle,plan_name,origin,enabled,accepted,sql_text from dba_sql_plan_baselines where
2 sql_text like 'select /*+ no_index(t2 idx_t2) */object_name%';
SQL_HANDLE PLAN_NAME ORIGIN ENA
------------------------------ ------------------------------ -------------- ---
ACC
---
SQL_TEXT
--------------------------------------------------------------------------------
SQL_75b06ae056223f5f SQL_PLAN_7bc3aw1b24guz24c6dbb6 MANUAL-LOAD YES
YES
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where object_id=4
10)验证
SQL> select * from table(dbms_xplan.display_cursor(null,null,'advanced'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 76td2qkxcrn9v, child number 1
-------------------------------------
select /*+ no_index(t2 idx_t2) */object_name,object_id from t2 where
object_id=4
Plan hash value: 2008370210
--------------------------------------------------------------------------------
------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|
--------------------------------------------------------------------------------
------
| 0 | SELECT STATEMENT | | | | 7 (100)|
|
| 1 | TABLE ACCESS BY INDEX ROWID| T2 | 1031 | 81449 | 7 (0)| 00:0
0:01 |
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|* 2 | INDEX RANGE SCAN | IDX_T2 | 412 | | 1 (0)| 00:0
0:01 |
--------------------------------------------------------------------------------
语句中是不走索引，但执行计划已经走了索引。