使用SPM固定执行计划
SQL Plan Management （简称SPM）
SPM是Oracle推荐使用的一种方法。使用起来也很简单。以下是一个手动固定执行计划的例子：
create table zzh_tb01 (id number, name varchar2(30));
create table zzh_tb02 (id number, name varchar2(30));
insert into zzh_tb01 values (1,'ahern');
insert into zzh_tb02 values (1,'zzh');
以如下语句为例，先执行该语句：
SQL> select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id;
ID NAME ID NAME
1 ahern 1 zzh
收集该查询语句的SQL_ID 以及 PLAN_HASH_VALUE ：
SQL> col sql_text for a60
SQL> select sql_id, hash_value, plan_hash_value, sql_text from v$sql where sql_text like 'select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id%';
SQL_ID HASH_VALUE PLAN_HASH_VALUE SQL_TEXT
37uy7rwzvm55y 1069126846 876607223 select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id
先确认一下目前该语句的执行计划：
SQL> select * from table(dbms_xplan.display_cursor(sql_id => '37uy7rwzvm55y'));
PLAN_TABLE_OUTPUT
SQL_ID 37uy7rwzvm55y, child number 0
select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id
Plan hash value: 876607223
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | | | 6 (100)| |
|* 1 | HASH JOIN | | 1 | 60 | 6 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
| 2 | TABLE ACCESS FULL| ZZH_TB01 | 1 | 30 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| ZZH_TB02 | 1 | 30 | 3 (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - access("A"."ID"="B"."ID")
Note
PLAN_TABLE_OUTPUT
- dynamic statistics used: dynamic sampling (level=2)
24 rows selected.
将该语句的cursor信息载入到Baseline中：
SQL> DECLARE
my_plans pls_integer;
BEGIN
my_plans := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE (sql_id => '37uy7rwzvm55y', plan_hash_value => '876607223');
END;
/
确认载入之后的状态：
SQL> col plan_name for a30
SQL> select sql_handle,plan_name, origin, enabled, accepted, fixed, reproduced, autopurge from dba_sql_plan_baselines where sql_text like 'select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id%';
SQL_HANDLE PLAN_NAME ORIGIN ENA ACC FIX REP AUT
SQL_8f0f55a93a637e86 SQL_PLAN_8y3upp4x66zn6dbf94702 MANUAL-LOAD-FROM-CURSOR-CACHE YES YES NO YES YES
注意：这里我们看 FIX 这列是 NO，说明目前该执行计划没有被固定。
执行如下语句将固定执行计划：
SQL> var res number
SQL> exec :res := DBMS_SPM.ALTER_SQL_PLAN_BASELINE (sql_handle => 'SQL_8f0f55a93a637e86', -
plan_name => 'SQL_PLAN_8y3upp4x66zn6dbf94702', -
attribute_name => 'FIXED', -
attribute_value => 'YES' );
PL/SQL procedure successfully completed.
再次来看baseline信息，FIX列已经变成了YES。
SQL> select sql_handle,plan_name, origin, enabled, accepted, fixed, reproduced, autopurge from dba_sql_plan_baselines where sql_text like 'select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id%';
SQL_HANDLE PLAN_NAME ORIGIN ENA ACC FIX REP AUT
SQL_8f0f55a93a637e86 SQL_PLAN_8y3upp4x66zn6dbf94702 MANUAL-LOAD-FROM-CURSOR-CACHE YES YES YES YES YES
这个时候我们再执行同样的语句，发现执行计划被固定并被查询使用，如下：
SQL> set autotrace on
SQL> select * from zzh_tb01 a, zzh_tb02 b where a.id = b.id;
ID NAME ID NAME
1 ahern 1 zzh
Execution Plan
Plan hash value: 876607223
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1 | 60 | 6 (0)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 60 | 6 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL| ZZH_TB01 | 1 | 30 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| ZZH_TB02 | 1 | 30 | 3 (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - access("A"."ID"="B"."ID")
Note
-
dynamic statistics used: dynamic sampling (level=2)
-
SQL plan baseline "SQL_PLAN_8y3upp4x66zn6dbf94702" used for this statement
-- 上述这里表明baseline SQL_PLAN_8y3upp4x66zn6dbf94702 被用于该语句 。
Statistics
998 recursive calls
65 db block gets
1287 consistent gets
7 physical reads
12204 redo size
777 bytes sent via SQL*Net to client
416 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
52 sorts (memory)
0 sorts (disk)
1 rows processed