[20170606]11G _optimizer_null_aware

[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
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SYS@book> @ &r/hide _optimizer_null_aware_antijoin
NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE
------------------------------ ----------------------------- ------------- ------------- ------------
_optimizer_null_aware_antijoin null-aware antijoin parameter TRUE TRUE TRUE

2.做一个测试例子:
SCOTT@book> create table t1 as select * from dba_objects;
Table created.

SCOTT@book> create table t2 as select * from dba_objects;
Table created.

SCOTT@book> select count(*) from t2;
COUNT(*)
----------
86996

SCOTT@book> select count(*) from t1;
COUNT(*)
----------
     86995
--//分析表略.
--//因为T1,T2建立有先后,这样T2的记录数量比T1记录的数量多1.注意1个特点允许NULL(这样建立的表),如果你使用all_objects来建立就情况不同了:
--//你可以查看定义desc all_objects, desc dba_objects.
SCOTT@book> @ &r/desc t1
   Name            Null? Type
   --------------- ----- --------------
1 OWNER                 VARCHAR2(30)
2 OBJECT_NAME           VARCHAR2(128)
3 SUBOBJECT_NAME        VARCHAR2(30)
4 OBJECT_ID             NUMBER
5 DATA_OBJECT_ID        NUMBER
6 OBJECT_TYPE           VARCHAR2(19)
7 CREATED               DATE
8 LAST_DDL_TIME         DATE
9 TIMESTAMP             VARCHAR2(19)
10 STATUS                VARCHAR2(7)
11 TEMPORARY             VARCHAR2(1)
12 GENERATED             VARCHAR2(1)
13 SECONDARY             VARCHAR2(1)
14 NAMESPACE             NUMBER
15 EDITION_NAME          VARCHAR2(30)

SCOTT@book> select * from t1 where object_name='T2';
no rows selected

SCOTT@book> select * from t2 where object_name='T2';
OWNER OBJECT_NAME SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE CREATED LAST_DDL_TIME TIMESTAMP STATUS T G S NAMESPACE EDITION_NAME
------ ----------- ---------- ---------- -------------- ----------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
SCOTT T2 90863 90863 TABLE 2017-06-06 16:12:27 2017-06-06 16:12:27 2017-06-06:16:12:27 VALID N N N 1

SCOTT@book> select * from t1 where OBJECT_ID=90863;
no rows selected

3.测试:
SCOTT@book> alter session set statistics_level=all;
Session altered.

SCOTT@book> select count(*) from t2 where object_id not in(select object_id from t1);
COUNT(*)
----------
0

SCOTT@book> select * from t2 where object_id not in(select object_id from t1);
no rows selected
--//why? 理论应该返回1行啊.

SCOTT@book> @ &r/dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 45ppus55apd1z, child number 1
-------------------------------------
select * from t2 where object_id not in(select object_id from t1)
Plan hash value: 35395643
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation               | Name | Starts | E-Rows |E-Bytes|E-Temp | Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads | OMem | 1Mem | Used-Mem |
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |      1 |        |       |       | 1218 (100)|          |      0 |00:00:00.06 |    1244 |   1242 |       |       |          |
|* 1 | HASH JOIN RIGHT ANTI NA|      |      1 |    870 | 89610 | 1448K| 1218   (1)| 00:00:15 |      0 |00:00:00.06 |    1244 |   1242 | 1696K| 1696K| 2503K (0)|
|   2 |   TABLE ACCESS FULL     | T1   |      1 | 86995 |   424K|       |   347   (1)| 00:00:05 | 86994 |00:00:00.02 |    1244 |   1242 |       |       |          |
|   3 |   TABLE ACCESS FULL     | T2   |      0 | 86996 | 8325K|       |   347   (1)| 00:00:05 |      0 |00:00:00.01 |       0 |      0 |       |       |          |
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T1@SEL$2
   3 - SEL$5DA710D3 / T2@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("OBJECT_ID"="OBJECT_ID")
27 rows selected.

--//这才想起来以前的一个错误,不能这样查询,因为IN中的记录存在NULL,这样NULL<>NULL.应该改写如下:

SCOTT@book> select * from t2 where object_id not in(select object_id from t1 where t1.object_id is not null );
OWNER OBJECT_NAME SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE CREATED LAST_DDL_TIME TIMESTAMP STATUS T G S NAMESPACE EDITION_NAME
------ -------------------- ---------- ---------- -------------- ------------------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
SCOTT T2 90863 90863 TABLE 2017-06-06 16:12:27 2017-06-06 16:12:27 2017-06-06:16:12:27 VALID N N N 1

SCOTT@book> @ &r/dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 9cn6amuwk12r4, child number 0
-------------------------------------
select * from t2 where object_id not in(select object_id from t1 where
t1.object_id is not null )
Plan hash value: 2323664790
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation                | Name | Starts | E-Rows |E-Bytes|E-Temp | Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads | OMem | 1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT         |      |      1 |        |       |       | 1218 (100)|          |      1 |00:00:00.15 |    2489 |   2484 |       |       |          |
|* 1 | HASH JOIN RIGHT ANTI SNA|      |      1 |    870 | 89610 | 1448K| 1218   (1)| 00:00:15 |      1 |00:00:00.15 |    2489 |   2484 | 5416K| 2890K| 5574K (0)|
|* 2 |   TABLE ACCESS FULL      | T1   |      1 | 86993 |   424K|       |   347   (1)| 00:00:05 | 86993 |00:00:00.02 |    1244 |   1242 |       |       |          |
|   3 |   TABLE ACCESS FULL      | T2   |      1 | 86996 | 8325K|       |   347   (1)| 00:00:05 | 86996 |00:00:00.03 |    1245 |   1242 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T1@SEL$2
   3 - SEL$5DA710D3 / T2@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("OBJECT_ID"="OBJECT_ID")
   2 - filter("T1"."OBJECT_ID" IS NOT NULL)
--//注意执行计划中的HASH JOIN RIGHT ANTI SNA.

4.测试"_optimizer_null_aware_antijoin"=false看看.

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

SCOTT@book> Select * from t2 where object_id not in(select object_id from t1 where t1.object_id is not null );
OWNER OBJECT_NAME SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE CREATED LAST_DDL_TIME TIMESTAMP STATUS T G S NAMESPACE EDITION_NAME
------ -------------------- ---------- ---------- -------------- ------------------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
SCOTT T2 90863 90863 TABLE 2017-06-06 16:12:27 2017-06-06 16:12:27 2017-06-06:16:12:27 VALID N N N 1
--//昏,那个慢受不了.......

SCOTT@book> @ &r/dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 4ps64yjz4g7pu, child number 0
-------------------------------------
Select * from t2 where object_id not in(select object_id from t1 where
t1.object_id is not null )
Plan hash value: 2132554994
------------------------------------------------------------------------------------------------------------------------------
| Id | Operation          | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads |
------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |      1 |        |       | 8847K(100)|          |      1 |00:04:06.56 |      53M|     67M|
|* 1 | FILTER            |      |      1 |        |       |            |          |      1 |00:04:06.56 |      53M|     67M|
|   2 |   TABLE ACCESS FULL| T2   |      1 | 86996 | 8325K|   347   (1)| 00:00:05 | 86996 |00:00:00.05 |    1245 |   1242 |
|* 3 |   TABLE ACCESS FULL| T1   | 86995 |      2 |    10 |   116   (0)| 00:00:02 | 86994 |00:04:05.95 |      53M|     67M|
------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1
   2 - SEL$1 / T2@SEL$1
   3 - SEL$2 / T1@SEL$2
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter( IS NULL)
   3 - filter(("T1"."OBJECT_ID" IS NOT NULL AND LNNVL("OBJECT_ID"<>:B1)))
29 rows selected.

3.换1个方式:

SCOTT@book> create table t11 as select * from all_objects;
Table created.

SCOTT@book> create table t22 as select * from all_objects;
Table created.
--//分析表略.

SCOTT@book> @ &r/desc t11
Name           Null?    Type
-------------- -------- ------------
OWNER          NOT NULL VARCHAR2(30)
OBJECT_NAME    NOT NULL VARCHAR2(30)
SUBOBJECT_NAME          VARCHAR2(30)
OBJECT_ID      NOT NULL NUMBER
DATA_OBJECT_ID          NUMBER
OBJECT_TYPE             VARCHAR2(19)
CREATED        NOT NULL DATE
LAST_DDL_TIME NOT NULL DATE
TIMESTAMP               VARCHAR2(19)
STATUS                  VARCHAR2(7)
TEMPORARY               VARCHAR2(1)
GENERATED               VARCHAR2(1)
SECONDARY               VARCHAR2(1)
NAMESPACE      NOT NULL NUMBER
EDITION_NAME            VARCHAR2(30)

--// 注意这样定义的表OBJECT_ID是非空.

SCOTT@book> select * from t22 where object_id not in(select object_id from t11);
OWNER OBJECT_NAME SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE CREATED LAST_DDL_TIME TIMESTAMP STATUS T G S NAMESPACE EDITION_NAME
------ -------------------- ---------- ---------- -------------- ------------------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
SCOTT T22 90869 90869 TABLE 2017-06-06 16:33:29 2017-06-06 16:33:29 2017-06-06:16:33:29 VALID N N N 1

SCOTT@book> @ &r/dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 31yq53mnd3g7k, child number 1
-------------------------------------
select * from t22 where object_id not in(select object_id from t11)
Plan hash value: 3941821364
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation            | Name | Starts | E-Rows |E-Bytes|E-Temp | Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads | OMem | 1Mem | Used-Mem |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |      1 |        |       |       | 1187 (100)|          |      1 |00:00:00.15 |    2427 |   2422 |       |       |          |
|* 1 | HASH JOIN RIGHT ANTI|      |      1 |    848 | 87344 | 1408K| 1187   (1)| 00:00:15 |      1 |00:00:00.15 |    2427 |   2422 | 5236K| 2890K| 5538K (0)|
|   2 |   TABLE ACCESS FULL | T11 |      1 | 84763 |   413K|       |   338   (1)| 00:00:05 | 84763 |00:00:00.02 |    1213 |   1211 |       |       |          |
|   3 |   TABLE ACCESS FULL | T22 |      1 | 84764 | 8112K|       |   338   (1)| 00:00:05 | 84764 |00:00:00.03 |    1214 |   1211 |       |       |          |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T11@SEL$2
   3 - SEL$5DA710D3 / T22@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("OBJECT_ID"="OBJECT_ID")

--//注意执行计划HASH JOIN RIGHT ANTI.我想起来以前10g我也遇到类型问题,将数据类型修改为NULL.

4.退出测试使用not exists的情况:

SCOTT@book> select * from t2 where not exists (select 1 from t1 where t1.OBJECT_ID=t2.object_id);
OWNER OBJECT_NAME SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE         CREATED             LAST_DDL_TIME       TIMESTAMP           STATUS T G S NAMESPACE EDITION_NAME
------ ----------- ---------- ---------- -------------- ------------------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
SCOTT T2                          90863          90863 TABLE               2017-06-06 16:12:27 2017-06-06 16:12:27 2017-06-06:16:12:27 VALID   N N N          1
PUBLIC LOOPBACK                                         DATABASE LINK       2016-12-14 15:17:00                                         VALID   N N N
PUBLIC TEST040                                          DATABASE LINK       2017-01-09 09:14:26                                         VALID   N N N
--//这样返回3条.也就是这样查询注意空值的情况.也就是要加入t2.object_id is not null 条件,才会返回1条.

SCOTT@book> @ &r/dpc '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID 4jx0g5ndct9vk, child number 0
-------------------------------------
select * from t2 where not exists (select 1 from t1 where
t1.OBJECT_ID=t2.object_id)
Plan hash value: 1142061071
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation            | Name | Starts | E-Rows |E-Bytes|E-Temp | Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads | OMem | 1Mem | Used-Mem |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |      1 |        |       |       | 1218 (100)|          |      3 |00:00:00.14 |    2489 |   2484 |       |       |          |
|* 1 | HASH JOIN RIGHT ANTI|      |      1 |    870 | 89610 | 1448K| 1218   (1)| 00:00:15 |      3 |00:00:00.14 |    2489 |   2484 | 5416K| 2890K| 5759K (0)|
|   2 |   TABLE ACCESS FULL | T1   |      1 | 86995 |   424K|       |   347   (1)| 00:00:05 | 86995 |00:00:00.02 |    1244 |   1242 |       |       |          |
|   3 |   TABLE ACCESS FULL | T2   |      1 | 86996 | 8325K|       |   347   (1)| 00:00:05 | 86996 |00:00:00.02 |    1245 |   1242 |       |       |          |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$5DA710D3
   2 - SEL$5DA710D3 / T1@SEL$2
   3 - SEL$5DA710D3 / T2@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")

SCOTT@book> select * from t1 where object_id is null ;
OWNER OBJECT_NAME          SUBOBJECT_ OBJECT_ID DATA_OBJECT_ID OBJECT_TYPE         CREATED             LAST_DDL_TIME       TIMESTAMP           STATUS T G S NAMESPACE EDITION_NAME
------ -------------------- ---------- ---------- -------------- ------------------- ------------------- ------------------- ------------------- ------- - - - ---------- ------------
PUBLIC LOOPBACK                                                  DATABASE LINK       2016-12-14 15:17:00                                         VALID   N N N
PUBLIC TEST040                                                   DATABASE LINK       2017-01-09 09:14:26                                         VALID   N N N
--//正好2条object_id is null.

5.总结:
1.再次注意not in 与NULL的查询.
2.建立良好的约束,规避一些这样的问题.

[20170606]11G _optimizer_null_aware_antijoin.txt的更多相关文章

【Oracle】跟踪文件目录(User_Dump_Dest)生成脚本（11g/9i).txt
oracle 11g 生成跟踪目录(User_Dump_Dest)脚本: –设置合适显示长度: column trace new_val TRACE format a100 –脚本: select c ...
11g手动打补丁
在两个节点上,分别以oracle用户执行,停止资源节点一: srvctl stop home -o /app/oracle/11g -s /home/oracle/s1 -n 11grac75 节 ...
转://从一条巨慢SQL看基于Oracle的SQL优化
http://mp.weixin.qq.com/s/DkIPwbDKIjH2FMN13GkT4w 本次分享的内容是基于Oracle的SQL优化,以一条巨慢的SQL为例,从快速解读SQL执行计划.如何从 ...
从一条巨慢SQL看基于Oracle的SQL优化(重磅彩蛋+PPT)
本文根据DBAplus社群第110期线上分享整理而成,文末还有好书送哦~ 讲师介绍丁俊新炬网络首席性能优化专家 SQL审核产品经理 DBAplus社群联合发起人.<剑破冰山-Oracle开发 ...
Linux内核配置选项
http://blog.csdn.net/wdsfup/article/details/52302142 http://www.manew.com/blog-166674-12962.html Gen ...
[20190416]11g下那些latch是Exclusive的.txt
[20190416]11g下那些latch是Exclusive的.txt --//昨天测试了11g下那些latch是共享的,链接:--//是否反过来剩下的都是Exclusive的.继续测试: 1.环境 ...
[20190415]11g下那些latch是共享的.txt
[20190415]11g下那些latch是共享的.txt http://andreynikolaev.wordpress.com/2010/11/23/shared-latches-by-oracl ...
[20190219]那个更快(11g).txt
[20190219]那个更快(11g).txt --//前几天测试11g Query Result Cache RC Latches时,链接http://blog.itpub.net/267265/v ...
[20190214]11g Query Result Cache RC Latches补充.txt
[20190214]11g Query Result Cache RC Latches补充.txt --//上午测试链接:http://blog.itpub.net/267265/viewspace- ...

随机推荐

java~springboot~h2数据库在单元测试中的使用
单元测试有几点要说的事实上springboot框架是一个tdd框架,你在进行建立项目时它会同时建立一个单元测试项目,而我们的代码用例可以在这个项目里完成,对于单元测试大叔有以下几点需要说明一下: 单 ...
java设计模式之——工厂模式
对于java的设计模式,我还是第一次认认真真的总结,以前用的时候都不曾留意细节,现在回头再看只知道该怎么设计,却忘记当时为嘛要用它了, 所以这次就做一个demo来再次复习总结一下,希望从中能学到新体悟 ...
Thrift架构介绍
Thrift是一个跨语言的服务部署框架,最初由Facebook于2007年开发,2008年进入Apache开源项目.Thrift通过一个中间语言(IDL, 接口定义语言)来定义RPC的接口和数据类型, ...
[CF286E] Ladies' shop
Description 给出 $n$ 个 $\leq m$ 且不同的数 $a_1,\dots,a_n$,现在要求从这 $n$ 个数中选出最少的数字,满足这 $n$ 个数字都可以由选 ...
Perl列表相关函数
内置的列表函数有: grep, join, map, qw//, reverse, sort, unpack join:将多个元素使用给定字符串联起来join grep:从列表中筛选符合条件的元素执行 ...
Go基础系列：接口类型断言和type-switch
接口类型探测:类型断言接口实例中存储了实现接口的类型实例,类型的实例有两种:值类型实例和指针类型实例.在程序运行过程中,接口实例存储的实例类型可能会动态改变.例如: // ins是接口实例 var ...
第一册：lesson seventeen。
原文:How do ;you do? A:Come and meet our employees,Mr.B. B:Thank you Mr.A. A:This is ...and this is .. ...
阿里云免费SSL证书申请与安装使用（IIS7）
准备: 阿里云已完成备案的域名一个第一步:免费SSL证书申请登陆阿里云平台,在域名控制台下,选择你的域名,点击“SSL”证书,如图所示再跳转后的页面,选择“单域名免费证书”,并补全域名,非二级域 ...
c# 判断3个数是否连续最优式子
Math.Abs((own - two) * (two - there) * + ) ==
Reactor模式理解
Reactor模式也可以叫反应器模式或者应答者模式 reactor模式简介让我们先了解一下阻塞I/O与非阻塞I/O I/O 是非常缓慢的 I/O绝对是计算机操作中最慢的.访问RAM的事件为ns级别 ...

[20170606]11G _optimizer_null_aware_antijoin.txt

[20170606]11G _optimizer_null_aware_antijoin.txt的更多相关文章

随机推荐

热门专题