[20130109]SPM与sql profile.txt
SPM是11G有的新特性,而sql profile在10g早已经存在。如果在11G,两者都使用的话,执行会选择那个呢?
自己做一个测试来说明情况:
1.建立测试环境:
2.我在执行计划中使用full提示,执行计划一定选择全表扫描:
我建立sql profile,方法如下:
--这样执行就是使用索引。先暂时禁用sql profile。
3.建立sql baseline:
--可以发现已经建立了sql baseline。使能sql profile。
4.两者都存在的情况下,会使用那个呢?
--可以从Note中发现,提示两者都使用,但是实际上执行计划使用的是全表扫描。也就是讲在两者都存在的情况下,SPM优先。
5.如果关闭SPM,看看:
--再次证明两者存在的情况下SPM优先,而不管那个执行效率高。
SPM是11G有的新特性,而sql profile在10g早已经存在。如果在11G,两者都使用的话,执行会选择那个呢?
自己做一个测试来说明情况:
1.建立测试环境:
SQL> select * from v$version where rownum
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
SQL> create table t as select rownum id ,lpad('x',100,'x') name from dual connect by level
Table created.
SQL> create unique index i_t_id on t(id);
SQL> exec dbms_stats.gather_table_stats(USER,'T',cascade => true);
SQL> variable a number ;
SQL> exec :a := 100;
SQL> select /*+ full(t) */ * from t where id = :a ;
2.我在执行计划中使用full提示,执行计划一定选择全表扫描:
我建立sql profile,方法如下:
DECLARE
ret_val VARCHAR2(4000);
BEGIN
ret_val := DBMS_SQLTUNE.CREATE_TUNING_TASK(
sql_id => '89u57qt97ftca',
plan_hash_value => NULL,
scope => 'COMPREHENSIVE',
time_limit => 1800,
task_name => 'test',
description => 'study');
Dbms_Sqltune.EXECUTE_TUNING_TASK('test');
END;
select Dbms_Sqltune.REPORT_TUNING_TASK('test', 'TEXT', 'all') report from dual
--提示执行如下:
execute dbms_sqltune.accept_sql_profile(task_name => 'test', task_owner=> 'SCOTT', replace => TRUE);
--这样执行就是使用索引。先暂时禁用sql profile。
BEGIN
DBMS_SQLTUNE.ALTER_SQL_PROFILE (
name => 'SYS_SQLPROF_013c1cf4e9920000',
attribute_name => 'STATUS',
value => 'DISABLED');
END;
3.建立sql baseline:
SQL> alter session set optimizer_capture_sql_plan_baselines=true ;
SQL> select /*+ full(t) */ * from t where id = :a ;
SQL> select /*+ full(t) */ * from t where id = :a ;
SQL> alter session set optimizer_capture_sql_plan_baselines=false ;
SQL> select sql_handle, plan_name, sql_text,enabled, accepted,fixed,origin,signature from dba_sql_plan_baselines ;
SQL_HANDLE PLAN_NAME SQL_TEXT ENA ACC FIX ORIGIN SIGNATURE
------------------------------ ------------------------------ -------------------------------------------------------- --- --- --- -------------- -----------------------
SYS_SQL_443d558815eb01e6 SQL_PLAN_48gapj0ayq0g694ecae5c select /*+ full(t) */ * from t where id = :a YES YES NO AUTO-CAPTURE 4917180411130085862
--可以发现已经建立了sql baseline。使能sql profile。
BEGIN
DBMS_SQLTUNE.ALTER_SQL_PROFILE (
name => 'SYS_SQLPROF_013c1cf4e9920000',
attribute_name => 'STATUS',
value => 'ENABLED');
END;
4.两者都存在的情况下,会使用那个呢?
SQL> select /*+ full(t) */ * from t where id = :a ;
ID NAME
---------- --------------------------------------------------
100 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
SQL> @dpc ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 89u57qt97ftca, child number 0
-------------------------------------
select /*+ full(t) */ * from t where id = :a
Plan hash value: 1601196873
--------------------------------------------------------
| Id | Operation | Name | E-Rows | Cost (%CPU)|
--------------------------------------------------------
| 0 | SELECT STATEMENT | | | 47 (100)|
|* 1 | TABLE ACCESS FULL| T | 1 | 47 (0)|
--------------------------------------------------------
Peeked Binds (identified by position):
--------------------------------------
1 - (NUMBER): 100
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("ID"=:A)
Note
-----
- SQL profile SYS_SQLPROF_013c1cf4e9920000 used for this statement
- SQL plan baseline SQL_PLAN_48gapj0ayq0g694ecae5c used for this statement
- Warning: basic plan statistics not available. These are only collected when:
* hint 'gather_plan_statistics' is used for the statement or
* parameter 'statistics_level' is set to 'ALL', at session or system level
31 rows selected.
--可以从Note中发现,提示两者都使用,但是实际上执行计划使用的是全表扫描。也就是讲在两者都存在的情况下,SPM优先。
5.如果关闭SPM,看看:
SQL> select sql_handle, plan_name, sql_text,enabled, accepted,fixed,origin,signature from dba_sql_plan_baselines ;
SQL_HANDLE PLAN_NAME SQL_TEXT ENA ACC FIX ORIGIN SIGNATURE
------------------------------ ------------------------------ -------------------------------------------------------- --- --- --- -------------- -----------------------
SYS_SQL_443d558815eb01e6 SQL_PLAN_48gapj0ayq0g694ecae5c select /*+ full(t) */ * from t where id = :a YES YES NO AUTO-CAPTURE 4917180411130085862
SYS_SQL_443d558815eb01e6 SQL_PLAN_48gapj0ayq0g6e3e62b6b select /*+ full(t) */ * from t where id = :a YES NO NO AUTO-CAPTURE 4917180411130085862
variable v_basenum number;
exec :v_basenum := dbms_spm.alter_sql_plan_baseline(sql_handle=>'SYS_SQL_443d558815eb01e6',plan_name=>'SQL_PLAN_48gapj0ayq0g694ecae5c',attribute_name=>'ENABLED',attribute_value=>'NO');
SQL> select sql_handle, plan_name, sql_text,enabled, accepted,fixed,origin,signature from dba_sql_plan_baselines ;
SQL_HANDLE PLAN_NAME SQL_TEXT ENA ACC FIX ORIGIN SIGNATURE
------------------------------ ------------------------------ -------------------------------------------------------- --- --- --- -------------- -----------------------
SYS_SQL_443d558815eb01e6 SQL_PLAN_48gapj0ayq0g694ecae5c select /*+ full(t) */ * from t where id = :a NO YES NO AUTO-CAPTURE 4917180411130085862
SYS_SQL_443d558815eb01e6 SQL_PLAN_48gapj0ayq0g6e3e62b6b select /*+ full(t) */ * from t where id = :a YES NO NO AUTO-CAPTURE 4917180411130085862
SQL> select /*+ full(t) */ * from t where id = :a ;
ID NAME
---------- --------------------------------------------------
100 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
SQL> @dpc ''
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------
SQL_ID 89u57qt97ftca, child number 0
-------------------------------------
select /*+ full(t) */ * from t where id = :a
Plan hash value: 1149237570
--------------------------------------------------------------------
| Id | Operation | Name | E-Rows | Cost (%CPU)|
--------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | 2 (100)|
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 | 2 (0)|
|* 2 | INDEX UNIQUE SCAN | I_T_ID | 1 | 1 (0)|
--------------------------------------------------------------------
Peeked Binds (identified by position):
--------------------------------------
1 - (NUMBER): 100
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("ID"=:A)
Note
-----
- SQL profile SYS_SQLPROF_013c1cf4e9920000 used for this statement
- Warning: basic plan statistics not available. These are only collected when:
* hint 'gather_plan_statistics' is used for the statement or
* parameter 'statistics_level' is set to 'ALL', at session or system level
--再次证明两者存在的情况下SPM优先,而不管那个执行效率高。