052011GR2 _optimizer_null_aware_antijoin

[20150520]11GR2 _optimizer_null_aware_antijoin.txt

--好久没写sql 优化的帖子:

http://www.killdb.com/2015/04/19/_optimizer_null_aware_antijoin%E5%BC%95%E5%8F%91%E7%9A%84sql%E6%80%A7%E8%83%BD%E9%97%AE%E9%A2%98.html

--参考这个链接自己重复测试看看在11G下的情况:

1.建立测试环境:

SCOTT@test> @ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.3.0     Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

create table t1
as select
cast(rownum as int) a,
cast(rownum+10 as int) b,
cast(dbms_random.string('i',10) as varchar2(10)) c
from dual connect by level 
create table t2
as select
cast(rownum as int) a,
cast(rownum+10 as int) b,
cast(dbms_random.string('i',10) as varchar2(10)) c
from dual connect by level

exec sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 't1',Estimate_Percent => NULL,Method_Opt => 'FOR ALL COLUMNS SIZE 1 ',Cascade => True ,No_Invalidate => false)
PL/SQL procedure successfully completed.

exec sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 't2',Estimate_Percent => NULL,Method_Opt => 'FOR ALL COLUMNS SIZE 1 ',Cascade => True ,No_Invalidate => false)
PL/SQL procedure successfully completed.

2.测试:

select /*SQL_1*/ c from t1 where a not in (select a from t2) ;

SCOTT@test> @dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  1war6t5g1w5g9, child number 0
-------------------------------------
select /*SQL_1*/ c from t1 where a not in (select a from t2)

Plan hash value: 895956251

---------------------------------------------------------------------------------------------------------------------
| Id  | Operation          | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
---------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |      1 |        |       | 40633 (100)|          |     20 |00:00:03.69 |     190K|
|*  1 |  FILTER            |      |      1 |        |       |            |          |     20 |00:00:03.69 |     190K|
|   2 |   TABLE ACCESS FULL| T1   |      1 |  10000 |   146K|     8   (0)| 00:00:01 |  10000 |00:00:00.01 |      37 |
|*  3 |   TABLE ACCESS FULL| T2   |  10000 |      1 |     4 |     8   (0)| 00:00:01 |   9980 |00:00:03.62 |     190K|
---------------------------------------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1
   2 - SEL$1 / T1@SEL$1
   3 - SEL$2 / T2@SEL$2

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

   1 - filter( IS NULL)
   3 - filter(LNNVL("A":B1))

--使用filter,逻辑读高达190K,效率低下.一般这种语句我会改写成not exists测试:

SCOTT@test> @dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  36gqqz0c26g8d, child number 0
-------------------------------------
select /*SQL_1*/ c from t1 where  not exists  (select a from t2 where
t2.a=t1.a)
Plan hash value: 629543484
--------------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation            | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
--------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |      1 |        |       |    17 (100)|          |     20 |00:00:00.08 |      73 |       |       |          |
|*  1 |  HASH JOIN RIGHT ANTI|      |      1 |     20 |   380 |    17   (6)| 00:00:01 |     20 |00:00:00.08 |      73 |  1517K|  1517K| 1872K (0)|
|   2 |   TABLE ACCESS FULL  | T2   |      1 |   9980 | 39920 |     8   (0)| 00:00:01 |   9980 |00:00:00.01 |      36 |       |       |          |
|   3 |   TABLE ACCESS FULL  | T1   |      1 |  10000 |   146K|     8   (0)| 00:00:01 |  10000 |00:00:00.01 |      37 |       |       |          |
--------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T2@SEL$2
   3 - SEL$5DA710D3 / T1@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("T2"."A"="T1"."A")

--很明显逻辑读73,以前有许多帖子讨论not in 与not exists那个好那个差,实际上现在许多情况下根本不需要考虑这些细节,oracle的查
--询转化很好的选择最优的执行方式.

3.使用sql profile看看:
--我写的脚本:
$ cat sp1.sql
set verify off
set long 20000000
set longchunksize  20000000
column report_tuning_task format a300
declare
  a varchar2(200);
begin
  a := dbms_sqltune.create_tuning_task(task_name=>'tuning &1',description=>'tuning sql_id=&1',scope=>dbms_sqltune.scope_comprehensive,time_limit=>1800,sql_id=>'&1');
  dbms_sqltune.execute_tuning_task( a );
end;
/

prompt
prompt =================================================================================================================================================
prompt tuning sql_id=&1 : report
prompt =================================================================================================================================================
select dbms_sqltune.report_tuning_task('tuning &1') report_tuning_task FROM dual;

prompt =================================================================================================================================================
prompt if finished,drop tuning task , run:
prompt execute dbms_sqltune.drop_tuning_task('tuning &1')
prompt if accept sql profile, run:
prompt execute dbms_sqltune.accept_sql_profile(task_name => 'tuning &1', replace => TRUE ,name=>'tuning &1');;
prompt execute dbms_sqltune.accept_sql_profile(task_name => 'tuning &1', replace => TRUE, name=>'tuning &1', FORCE_MATCH=>True)
prompt if drop or alter sql profile ,run :
prompt execute dbms_sqltune.drop_sql_profile(name => 'tuning &1')
prompt execute dbms_sqltune.alter_sql_profile(name => 'tuning &1',attribute_name=>'STATUS',value=>'DISABLED')
prompt =================================================================================================================================================
prompt
prompt
set serveroutput off

SCOTT@test> @sp1 1war6t5g1w5g9
PL/SQL procedure successfully completed.

=================================================================================================================================================
tuning sql_id=1war6t5g1w5g9 : report
=================================================================================================================================================
REPORT_TUNING_TASK
-------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name   : tuning 1war6t5g1w5g9
Tuning Task Owner  : SCOTT
Workload Type      : Single SQL Statement
Scope              : COMPREHENSIVE
Time Limit(seconds): 1800
Completion Status  : COMPLETED
Started at         : 05/20/2015 09:35:56
Completed at       : 05/20/2015 09:36:03

-------------------------------------------------------------------------------
Schema Name: SCOTT
SQL ID     : 1war6t5g1w5g9
SQL Text   : select /*SQL_1*/ c from t1 where a not in (select a from t2)

-------------------------------------------------------------------------------
FINDINGS SECTION (2 findings)
-------------------------------------------------------------------------------

1- SQL Profile Finding (see explain plans section below)
--------------------------------------------------------
  A potentially better execution plan was found for this statement.

  Recommendation (estimated benefit: 99.95%)
  ------------------------------------------
  - Consider accepting the recommended SQL profile.
    execute dbms_sqltune.accept_sql_profile(task_name => 'tuning
            1war6t5g1w5g9', task_owner => 'SCOTT', replace => TRUE);

  Validation results
  ------------------
  The SQL profile was tested by executing both its plan and the original plan
  and measuring their respective execution statistics. A plan may have been
  only partially executed if the other could be run to completion in less time.

                           Original Plan  With SQL Profile  % Improved
                           -------------  ----------------  ----------
  Completion Status:            COMPLETE          COMPLETE
  Elapsed Time (s):            3.733955           .082431      97.79 %
  CPU Time (s):                3.734431           .082387      97.79 %
  User I/O Time (s):                  0                 0
  Buffer Gets:                   190911                72      99.96 %
  Physical Read Requests:             0                 0
  Physical Write Requests:            0                 0
  Physical Read Bytes:                0                 0
  Physical Write Bytes:               0                 0
  Rows Processed:                    20                20
  Fetches:                           20                20
  Executions:                         1                 1

  Notes
  -----
  1. Statistics for the original plan were averaged over 1 executions.
  2. Statistics for the SQL profile plan were averaged over 10 executions.

2- Restructure SQL finding (see plan 1 in explain plans section)
----------------------------------------------------------------
  The optimizer could not unnest the subquery at line ID 1 of the execution
  plan.

  Recommendation
  --------------
  - Consider replacing "NOT IN" with "NOT EXISTS" or ensure that columns used
    on both sides of the "NOT IN" operator are declared "NOT NULL" by adding
    either "NOT NULL" constraints or "IS NOT NULL" predicates.

-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------

1- Original With Adjusted Cost
------------------------------
Plan hash value: 895956251

---------------------------------------------------------------------------
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |  9999 |   146K| 40633   (2)| 00:00:01 |
|*  1 |  FILTER            |      |       |       |            |          |
|   2 |   TABLE ACCESS FULL| T1   | 10000 |   146K|     8   (0)| 00:00:01 |
|*  3 |   TABLE ACCESS FULL| T2   |     1 |     4 |     8   (0)| 00:00:01 |
---------------------------------------------------------------------------

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

   1 - filter( NOT EXISTS (SELECT /*+ FULL ("T2") */ 0 FROM "T2" "T2"
              WHERE LNNVL("A":B1)))
   3 - filter(LNNVL("A":B1))

2- Using SQL Profile
--------------------
Plan hash value: 2739594415

--------------------------------------------------------------------------------
| Id  | Operation               | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |   100 |  1900 |    17   (6)| 00:00:01 |
|*  1 |  HASH JOIN RIGHT ANTI NA|      |   100 |  1900 |    17   (6)| 00:00:01 |
|   2 |   TABLE ACCESS FULL     | T2   |  9980 | 39920 |     8   (0)| 00:00:01 |
|   3 |   TABLE ACCESS FULL     | T1   | 10000 |   146K|     8   (0)| 00:00:01 |
--------------------------------------------------------------------------------

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

   1 - access("A"="A")

-------------------------------------------------------------------------------

=================================================================================================================================================
if finished,drop tuning task , run:
execute dbms_sqltune.drop_tuning_task('tuning 1war6t5g1w5g9')
if accept sql profile, run:
execute dbms_sqltune.accept_sql_profile(task_name => 'tuning 1war6t5g1w5g9', replace => TRUE ,name=>'tuning 1war6t5g1w5g9');
execute dbms_sqltune.accept_sql_profile(task_name => 'tuning 1war6t5g1w5g9', replace => TRUE, name=>'tuning 1war6t5g1w5g9', FORCE_MATCH=>True)
if drop or alter sql profile ,run :
execute dbms_sqltune.drop_sql_profile(name => 'tuning 1war6t5g1w5g9')
execute dbms_sqltune.alter_sql_profile(name => 'tuning 1war6t5g1w5g9',attribute_name=>'STATUS',value=>'DISABLED')
=================================================================================================================================================

--注意看
  Recommendation
  --------------
  - Consider replacing "NOT IN" with "NOT EXISTS" or ensure that columns used
    on both sides of the "NOT IN" operator are declared "NOT NULL" by adding
    either "NOT NULL" constraints or "IS NOT NULL" predicates.

--注意看以上提示,再次说明一些约束对控制执行计划的好处执行计划.执行如下稳定执行计划:

SCOTT@test> execute dbms_sqltune.accept_sql_profile(task_name => 'tuning 1war6t5g1w5g9', replace => TRUE ,name=>'tuning 1war6t5g1w5g9');
PL/SQL procedure successfully completed.

SCOTT@test> select /*SQL_1*/ c from t1 where  not exists  (select a from t2 where t2.a=t1.a) ;

SCOTT@test> @dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  1war6t5g1w5g9, child number 0
-------------------------------------
select /*SQL_1*/ c from t1 where a not in (select a from t2)
Plan hash value: 2739594415
-----------------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |      1 |        |       |    17 (100)|          |     20 |00:00:00.08 |      73 |       |       |          |
|*  1 |  HASH JOIN RIGHT ANTI NA|      |      1 |    100 |  1900 |    17   (6)| 00:00:01 |     20 |00:00:00.08 |      73 |  1517K|  1517K| 1852K (0)|
|   2 |   TABLE ACCESS FULL     | T2   |      1 |   9980 | 39920 |     8   (0)| 00:00:01 |   9980 |00:00:00.01 |      36 |       |       |          |
|   3 |   TABLE ACCESS FULL     | T1   |      1 |  10000 |   146K|     8   (0)| 00:00:01 |  10000 |00:00:00.01 |      37 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T2@SEL$2
   3 - SEL$5DA710D3 / T1@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("A"="A")
Note
-----
   - SQL profile tuning 1war6t5g1w5g9 used for this statement

--说明SQL PROFILE已经起作用.注意一些细节,这个执行计划与not exists是有一点小小的不同.HASH JOIN RIGHT ANTI NA.

4.看看sql profile使用的提示:

SCOTT@test> @hide _optimizer_null_aware_antijoin
NAME                            DESCRIPTION                    DEFAULT_VALUE  SESSION_VALUE  SYSTEM_VALUE
------------------------------- ------------------------------ -------------- -------------- -------------
_optimizer_null_aware_antijoin  null-aware antijoin parameter  TRUE           FALSE          FALSE

$ cat spext.sql
/* Formatted on 2015/4/10 17:03:49 (QP5 v5.252.13127.32867) */
column hint format a150
column name format a30
SELECT EXTRACTVALUE (VALUE (h), '.') AS hint,so.name
  FROM SYS.sqlobj$data od
      ,SYS.sqlobj$ so
      ,TABLE
       (
          XMLSEQUENCE
          (
             EXTRACT (XMLTYPE (od.comp_data), '/outline_data/hint')
          )
       ) h
WHERE     so.NAME in ( 'profile &&1', 'tuning &&1','switch tuning &&1')
       AND so.signature = od.signature
       AND so.CATEGORY = od.CATEGORY
       AND so.obj_type = od.obj_type
       AND so.plan_id = od.plan_id;

SCOTT@test> @spext 1war6t5g1w5g9
HINT                                   NAME
-------------------------------------- ------------------------------
OPTIMIZER_FEATURES_ENABLE(default)     tuning 1war6t5g1w5g9

--昏,提示仅仅是OPTIMIZER_FEATURES_ENABLE(default).

5.最后测试作者提到的隐含参数:

--drop sql profile.

SCOTT@test> execute dbms_sqltune.drop_sql_profile(name => 'tuning 1war6t5g1w5g9')
PL/SQL procedure successfully completed.

SCOTT@test> alter session set "_optimizer_null_aware_antijoin"=true;
Session altered.

SCOTT@test> @dpc '' ''
PLAN_TABLE_OUTPUT
--------------------------------------
SQL_ID  1war6t5g1w5g9, child number 1
-------------------------------------
select /*SQL_1*/ c from t1 where a not in (select a from t2)
Plan hash value: 2739594415
-----------------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |      1 |        |       |    17 (100)|          |     20 |00:00:00.08 |      73 |       |       |          |
|*  1 |  HASH JOIN RIGHT ANTI NA|      |      1 |     20 |   380 |    17   (6)| 00:00:01 |     20 |00:00:00.08 |      73 |  1517K|  1517K| 1886K (0)|
|   2 |   TABLE ACCESS FULL     | T2   |      1 |   9980 | 39920 |     8   (0)| 00:00:01 |   9980 |00:00:00.01 |      36 |       |       |          |
|   3 |   TABLE ACCESS FULL     | T1   |      1 |  10000 |   146K|     8   (0)| 00:00:01 |  10000 |00:00:00.01 |      37 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T2@SEL$2
   3 - SEL$5DA710D3 / T1@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("A"="A")

SCOTT@test> alter session set "_optimizer_null_aware_antijoin"=false;
Session altered.

6.加入非NULL看看情况如何?

SCOTT@test> alter table t1 modify a not null;
Table altered.

SCOTT@test> alter table t2 modify a not null;
Table altered.

SCOTT@test> select /*SQL_1*/ c from t1 where a not in (select a from t2) ;

SCOTT@test> @dpc '' ''
PLAN_TABLE_OUTPUT
--------------------------------------
SQL_ID  1war6t5g1w5g9, child number 0
-------------------------------------
select /*SQL_1*/ c from t1 where a not in (select a from t2)
Plan hash value: 629543484
--------------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation            | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
--------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |      1 |        |       |    17 (100)|          |     20 |00:00:00.08 |      73 |       |       |          |
|*  1 |  HASH JOIN RIGHT ANTI|      |      1 |     20 |   380 |    17   (6)| 00:00:01 |     20 |00:00:00.08 |      73 |  1517K|  1517K| 1830K (0)|
|   2 |   TABLE ACCESS FULL  | T2   |      1 |   9980 | 39920 |     8   (0)| 00:00:01 |   9980 |00:00:00.01 |      36 |       |       |          |
|   3 |   TABLE ACCESS FULL  | T1   |      1 |  10000 |   146K|     8   (0)| 00:00:01 |  10000 |00:00:00.01 |      37 |       |       |          |
--------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T2@SEL$2
   3 - SEL$5DA710D3 / T1@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("A"="A")

--注意id1:HASH JOIN RIGHT ANTI.

--总结:
--可以发现选择很好的执行计划,正像作者讲的那样,数据结构设计在这里起了很关键的作用,如果在一些细节上处理好,就可以避免许多性
--能问题.另外注意not in,not exists,或者in,exist的语句里面的sql语句,如果存在性能问题,可以试着在这些字段上确定是否为非空,
--加入一些约束也许能改变执行机会,取得好的优化效果.

时间： 2024-10-14 23:25:18

052011GR2 _optimizer_null_aware_antijoin的相关文章

浅析_optimizer_null_aware_antijoin引发的SQL性能问题

前几天某客户联系我说之前我们进行存储迁移的系统,有个SQL跑的极慢,根本跑不出来结果.通过VPN登录看了下,SQL确认跑的很慢.开始我很难理解,我们仅仅是进行了存储迁移,数据库基本上没动,为什么会有SQL性能问题呢?  我们先来看看有问题的SQL: SYS@rptdb1> set autot traceonly exp SYS@rptdb1> select a.*,b.rate TAX_RATE,round(a.charge*b.rate/(1+b.rate),0) tax,a.charge-

060611G _optimizer_null_aware_antijoin

[20170606]11G _optimizer_null_aware_antijoin.txt --//上午测试_optimizer_null_aware_antijoin,发现自己不经意间又犯了一个低级错误,做1个记录. 1.环境: SYS@book> @ &r/ver1 PORT_STRING                    VERSION        BANNER ------------------------------ -------------- ----------

Oracle 12.1 RAC安装新主机，识别老存储和恢复数据库例子

具体步骤如下(因为先在12.1中测试,然后才在112.测试,因此这里的测试记录了发现的一些问题和处理方法,而11.2中模拟主机损坏,直接使用了这里的经验,因此没有任何报错信息): 1,安装12.1.0.2的GI软件,如果需要也apply最新的PSU,然后查看磁盘和磁盘组: [grid@lunarrac ~]$ kfod disks=all ds=true cluster=true status=true ----------------------------------------------

杀手SQL- 一条关于 'Not in' SQL 的优化案例

编辑手记:在 DBA 所优化的数据库环境中,绝大多数性能问题其实是由于 SQL 编写不当导致的.SQL 的世界无奇不有,今天我们一起见识一条让你绝对想吐血的杀手SQL. 某保险客户,ETL 耗时数个小时,我们做了sql report发现压力主要在其中一个SQL上. 单次执行时间:5788(秒) 单次逻辑读:10亿(块) 单次返回行数:21万(行) 我们首先看SQL语句,因为比较长,此处只节选部分的 查看其执行计划: 我们主要关注一下从7到16行:发现存在两次全表扫描.中间做了一次filter.

《Oracle高性能SQL引擎剖析：SQL优化与调优机制详解》一2.4　执行计划各个操作的含义

2.4 执行计划各个操作的含义 通常我们所说的执行计划操作包含两个部分:操作与其选项.例如,哈希关联反关联(HASH JOIN ANTI)中,哈希关联(HASH JOIN)是一种操作,"反"关联(ANTI)则是其选项:该操作还可以与其他选项(如"半"关联,SEMI)配合形成不同的执行计划操作. 执行计划中的操作数量非常多.我们下面列出的操作是Oracle 10gR2中的绝大多数操作.Oracle的每个版本都会有一些新的特性出现,而其中一些新特性又会带来新的操作,或者

20160318了解oracle版本升级的一些参数变化

[20160318]了解oracle版本升级的一些参数变化.txt --曾经写过一篇了解oracle版本升级后一些参数变化,可以通过如下连接了解: http://blog.itpub.net/267265/viewspace-1655594/ --实际上还有一个简单的方法就是提示opt_param('optimizer_features_enable' '11.2.0.1') ,然后顺便执行一条sql语句,查看执行计 --划就可以那些参数发生了变化.通过例子说明: 1.环境: SCOTT@boo

[20150515]简单了解某个版本有什么新特性

[20150515]简单了解某个版本有什么新特性.txt --如果想简单的了解某个版本的新特性,可以设置optimizer_features_enable SCOTT@test> show parameter optimizer_features_enable NAME                                 TYPE    VALUE ------------------------------------ ------- -------- optimizer_feat

1014OPT_PARAM OPTIMIZER_FEATURES_ENABLE

[20141014]OPT_PARAM与OPTIMIZER_FEATURES_ENABLE.txt http://www.itpub.net/thread-1495845-1-1.html http://space.itpub.net/267265/viewspace-723066 http://blog.itpub.net/267265/viewspace-752117/ http://blog.itpub.net/267265/viewspace-1298186/ --上午写了一篇blog,

Oracle 隐含参数

Oracle 隐含参数 点击(此处)折叠或打开 set pagesize 9999 set line 9999 col NAME format a40 col KSPPDESC format a50 col KSPPSTVL format a20 SELECT a.INDX,        a.KSPPINM NAME,        a.KSPPDESC,        b.KSPPSTVL FROM x$ksppi a,        x$ksppcv b WHERE a.INDX = b.