[20170604]12c Top Frequency histogram补充.txt

1.环境:
SCOTT@test01p> @　ver1
PORT_STRING                    VERSION        BANNER                                                                               CON_ID
------------------------------ -------------- -------------------------------------------------------------------------------- ----------
IBMPC/WIN_NT64-9.1.0           12.1.0.1.0     Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production              0

--//如果要建立Top Frequency histogram必须要满足几个条件:
--//链接 raajeshwaran.blogspot.co.id/2016/06/top-frequency-histogram-in-12c.html

The database creates a Top frequency histogram, when the following criteria are met.

NDV is greater than n, where n is the requested number of buckets (default 254)
The percentage of rows occupied by Top-frequent values is greater than or equal to the threshold p where p is (1-(1/n)*100).
The estimate_percent parameter in dbms_stats gathering procedure should be auto_sample_size (set to default)

SCOTT@test01p> create table t as select * from dba_objects;
Table created.

select column_name,num_distinct,density,histogram,SAMPLE_SIZE
  from user_tab_col_statistics
  where table_name ='T'
  and column_name ='OWNER';

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32     .03125 NONE                  91695

--//12c ctas 建立统计信息,但是不会建立直方图.density 1/32=.03125.
SCOTT@test01p> select count(*) from t;
  COUNT(*)
----------
     91695

--//随手写的sql语句:
with a as (select distinct owner,count(*) over(partition by owner) n1 ,count(*) over () n2 from t order by 2 desc ),
b as (select owner,n1,n2,sum(n1) over (order by n1 desc) n3  from a order by n1 desc)
select rownum,owner,n1,n2,n3,round(n3/n2,5) x1,round(1-1/rownum,5) x2 from b;

ROWNUM OWNER                N1         N2         N3         X1         X2
------ ----------------- ----- ---------- ---------- ---------- ----------
     1 SYS               41942      91695      41942     .45741          0
     2 PUBLIC            37142      91695      79084     .86247         .5
     3 APEX_040200        3405      91695      82489      .8996     .66667
     4 ORDSYS             3157      91695      85646     .93403        .75
     5 MDSYS              1819      91695      87465     .95387         .8
     6 XDB                 985      91695      88450     .96461     .83333
     7 SYSTEM              641      91695      89091      .9716     .85714
     8 CTXSYS              405      91695      89496     .97602       .875
     9 WMSYS               387      91695      89883     .98024     .88889
    10 DVSYS               352      91695      90235     .98408         .9
    11 SH                  309      91695      90544     .98745     .90909
    12 ORDDATA             292      91695      90836     .99063     .91667
    13 LBACSYS             209      91695      91045     .99291     .92308
    14 OE                  142      91695      91187     .99446     .92857
    15 SCOTT                96      91695      91283     .99551     .93333
    16 GSMADMIN_INTERNAL    77      91695      91360     .99635      .9375
    17 IX                   58      91695      91418     .99698     .94118
    18 DBSNMP               55      91695      91473     .99758     .94444
    19 PM                   44      91695      91517     .99806     .94737
    20 HR                   35      91695      91552     .99844        .95
    21 OLAPSYS              25      91695      91577     .99871     .95238
    22 OJVMSYS              23      91695      91600     .99896     .95455
    23 DVF                  19      91695      91619     .99917     .95652
    24 FLOWS_FILES          13      91695      91632     .99931     .95833
    25 AUDSYS               12      91695      91644     .99944        .96
    26 ORDPLUGINS           10      91695      91664     .99966     .96154
    27 OUTLN                10      91695      91664     .99966     .96296
    28 BI                    8      91695      91688     .99992     .96429
    29 ORACLE_OCM            8      91695      91688     .99992     .96552
    30 SI_INFORMTN_SCHEM     8      91695      91688     .99992     .96667
    31 APPQOSSYS             5      91695      91693     .99998     .96774
    32 TEST                  2      91695      91695          1     .96875

D:\temp>cat a1.sql
cat a1.sql
exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size &1');
select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';

SCOTT@test01p> @ a1.sql 2
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32     .03125 HYBRID                 5500

SCOTT@test01p> @ a1.sql 3
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 5.4529E-06 TOP-FREQUENCY         91695

SCOTT@test01p> @ a1.sql 4
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 5.4529E-06 TOP-FREQUENCY         91695

SCOTT@test01p> @ a1.sql 31
PL/SQL procedure successfully completed.
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 5.4529E-06 TOP-FREQUENCY         91695

SCOTT@test01p> @ a1.sql 32
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 5.4529E-06 FREQUENCY             91695

--//除了bucket=2,32建立的直方图HYBRID,FREQUENCY外,建立的都是TOP-FREQUENCY.
--//以10个bucket为例.解方程式(90235-x)/(91695-x)=0.9 ,得到x=77095.也就是要减少77095.

--//delete t where owner='SYS' and rownum<=41000;
--//delete t where owner='PUBLIC' and rownum<=36095;

SCOTT@test01p> delete t where owner='SYS' and rownum<=41000;
41000 rows deleted.

SCOTT@test01p> delete t where owner='PUBLIC' and rownum<=36095;
36095 rows deleted.

SCOTT@test01p> commit ;
Commit complete.

with a as (select distinct owner,count(*) over(partition by owner) n1 ,count(*) over () n2 from t order by 2 desc ),
b as (select owner,n1,n2,sum(n1) over (order by n1 desc) n3  from a order by n1 desc)
select rownum,owner,n1,n2,n3,round(n3/n2,5) x1,round(1-1/rownum,5) x2 from b where rownum<=11;

ROWNUM OWNER         N1         N2         N3         X1         X2
------ ----------- ---- ---------- ---------- ---------- ----------
     1 APEX_040200 3405      14600       3405     .23322          0
     2 ORDSYS      3157      14600       6562     .44945         .5
     3 MDSYS       1819      14600       8381     .57404     .66667
     4 PUBLIC      1047      14600       9428     .64575        .75
     5 XDB          985      14600      10413     .71322         .8
     6 SYS          942      14600      11355     .77774     .83333
     7 SYSTEM       641      14600      11996     .82164     .85714
     8 CTXSYS       405      14600      12401     .84938       .875
     9 WMSYS        387      14600      12788     .87589     .88889
    10 DVSYS        352      14600      13140         .9         .9
    11 SH           309      14600      13449     .92116     .90909
11 rows selected.
--//backet=10,前面10个值占90%.

SCOTT@test01p> @ a1 10
PL/SQL procedure successfully completed.
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 .000034247 TOP-FREQUENCY         14600

--//再减少1条记录.
SCOTT@test01p> delete t where owner='SYS' and rownum<=1;
1 row deleted.

SCOTT@test01p> commit ;
Commit complete.

ROWNUM OWNER         N1         N2         N3         X1         X2
------ ----------- ---- ---------- ---------- ---------- ----------
     1 APEX_040200 3405      14599       3405     .23324          0
     2 ORDSYS      3157      14599       6562     .44948         .5
     3 MDSYS       1819      14599       8381     .57408     .66667
     4 PUBLIC      1047      14599       9428      .6458        .75
     5 XDB          985      14599      10413     .71327         .8
     6 SYS          941      14599      11354     .77772     .83333
     7 SYSTEM       641      14599      11995     .82163     .85714
     8 CTXSYS       405      14599      12400     .84937       .875
     9 WMSYS        387      14599      12787     .87588     .88889
    10 DVSYS        352      14599      13139     .89999         .9
    11 SH           309      14599      13448     .92116     .90909
11 rows selected.
--//现在前10占.89999.

SCOTT@test01p> @ a1 10
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32    .018378 HYBRID                14599

--//可以发现建立的直方图不是TOP-FREQUENCY,而是HYBRID(混合型直方图).
--//转化成TOP-FREQUENCY.
SCOTT@test01p> insert into t  select * from dba_objects where owner='SYS' and rownum=1;
1 row created.

SCOTT@test01p> commit ;
Commit complete.

SCOTT@test01p> @ a1 10
PL/SQL procedure successfully completed.

COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 .000034247 TOP-FREQUENCY         14600

--//以上内容是昨天的测试.
--//前面我提到如果取样不是auto_sample_size,也可能不行,测试看看.

2.取样大小Estimate_Percent  => NULL.
SCOTT@test01p> exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size 10',Estimate_Percent  => NULL);
PL/SQL procedure successfully completed.

SCOTT@test01p> select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32    .018379 HYBRID                14600

--//可以发现如果全取样,反而生成混合型直方图.

3.取样大小Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE,Block_sample => TRUE.
SCOTT@test01p> exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size 10',Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE,Block_sample => TRUE);
PL/SQL procedure successfully completed.

SCOTT@test01p> select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 .000034247 TOP-FREQUENCY         14600

--//可以发现Estimate_Percent=>SYS.DBMS_STATS.AUTO_SAMPLE_SIZE,不管是块取样依旧.

4.取样Estimate_Percent  => 100,90看看.
SCOTT@test01p> exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size 10',Estimate_Percent  => 100);
PL/SQL procedure successfully completed.

SCOTT@test01p> select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 .062908991 HEIGHT BALANCED       14600

SCOTT@test01p> exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size 10',Estimate_Percent  => 90);
PL/SQL procedure successfully completed.

SCOTT@test01p> select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32      .0625 HEIGHT BALANCED       13108

--//看来仅仅Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE才会生成TOP-FREQUENCY直方图.
SCOTT@test01p> exec  dbms_stats.gather_table_stats(ownname=>user,tabname=>'T',method_opt=>'for columns owner size 10',Estimate_Percent  => SYS.DBMS_STATS.AUTO_SAMPLE_SIZE);
PL/SQL procedure successfully completed.

SCOTT@test01p> select column_name,num_distinct,density,histogram,SAMPLE_SIZE from user_tab_col_statistics where table_name ='T' and column_name ='OWNER';
COLUMN_NAME          NUM_DISTINCT    DENSITY HISTOGRAM       SAMPLE_SIZE
-------------------- ------------ ---------- --------------- -----------
OWNER                          32 .000034247 TOP-FREQUENCY         14600

--//有机会研究HYBRID直方图.

[20170604]12c Top Frequency histogram补充.txt的更多相关文章

  1. [20170603]12c Top Frequency histogram.txt

    ---恢复内容开始--- [20170603]12c Top Frequency histogram.txt --//个人对直方图了解很少,以前2种直方图类型对于目前的许多应用来讲已经足够,或者讲遇到 ...

  2. [20180928]ora-01426(补充).txt

    [20180928]ora-01426(补充).txt --//链接:http://www.itpub.net/thread-2105458-1-1.html--//做一点点必要的补充: 1.环境:S ...

  3. [20170916]sqlplus set array最小2补充.txt

    [20170916]sqlplus set array最小2补充.txt --//以前写的贴子,链接http://blog.itpub.net/267265/viewspace-1453652/--/ ...

  4. [20190312]关于增量检查点的疑问(补充).txt

    [20190312]关于增量检查点的疑问(补充).txt --//有人问我以前写一个帖子的问题,关于增量检查点的问题,链接如下:http://blog.itpub.net/267265/viewspa ...

  5. [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- ...

  6. [20181108]12c sqlplus rowfetch参数4.txt

    [20181108]12c sqlplus rowfetch参数4.txt --//12cR2 可以改变缺省rowfetch参数.11g之前缺省是1.通过一些测试说明问题.--//前几天做的测试有点乱 ...

  7. [20181031]12c 在线移动数据文件.txt

    [20181031]12c 在线移动数据文件.txt --//12c以前,移动或者改名数据文件是一项比较麻烦的事情,至少要停一下业务.而12c支持在线移动或者改名数据文件,并且有点不可思议--//的是 ...

  8. [20171107]dbms_shared_pool.pin补充.txt

    [20171107]dbms_shared_pool.pin补充.txt --//上午的测试,做一些补充,主要还是一些理解问题. 1.环境:SCOTT@book> @ &r/ver1 P ...

  9. top 自动执行的shell脚本中，使用top -n 1 > log.txt, 上电自动执行，文件无输出

    . 自动执行的shell脚本中,使用top -n > log.txt, 上电自动执行,文件无输出,使用一下命令解决: //usr/bin/top -d -n -b > log.txt 如果 ...

随机推荐

  1. 【HDFS API编程】第一个应用程序的开发-创建文件夹

    /** * 使用Java API操作HDFS文件系统 * 关键点: * 1)创建 Configuration * 2)获取 FileSystem * 3)...剩下的就是 HDFS API的操作了*/ ...

  2. MongoDB从入门到优化

    目录 一.MongoDB 简介 二.MongoDB 的储存引擎 三.mongodb 配置参数 四.MongoDB 单节点搭建 五.MongoDB 连接 六.MongoDB 常用命令 七.MongoDB ...

  3. ABP框架是怎么一回事呢？

    ABP(ASP.NET Boilerplate['bɔɪlɚplet]:样板文件),就是一套基于.Net开源框架,官方地址为:https://aspnetboilerplate.com/ , 在这个地 ...

  4. Mysql加锁过程详解（7）-初步理解MySQL的gap锁

    Mysql加锁过程详解(1)-基本知识 Mysql加锁过程详解(2)-关于mysql 幻读理解 Mysql加锁过程详解(3)-关于mysql 幻读理解 Mysql加锁过程详解(4)-select fo ...

  5. java基础系列--volatile关键字

    原创作品,可以转载,但是请标注出处地址:http://www.cnblogs.com/V1haoge/p/7833881.html 1.volatile简述 据说,volatile是java语言中最轻 ...

  6. Python获得百度统计API的数据并发送邮件

    Python获得百度统计API的数据并发送邮件 小工具  本来这么晚是不准备写博客的,当是想到了那个狗子绝对会在开学的时候跟我逼逼这个事情,所以,还是老老实实地写一下吧.   Baidu统计API的使 ...

  7. MySQL中间件之ProxySQL(4)：多层配置系统

    返回ProxySQL系列文章:http://www.cnblogs.com/f-ck-need-u/p/7586194.html 1.ProxySQL中的库 使用ProxySQL的Admin管理接口连 ...

  8. redis的Pub/Sub

    redis的Pub/Sub机制类似于广播架构,Subscriber相当于收音机,可以收听多个channel(频道),Publisher(电台)可以在channel中发布信息. 命令介绍 PUBLISH ...

  9. C#面向对象之多态。

    1.定义:指不同的对象收到相同的消息时,会产生不同的行为,同一个类在不同的场合下表现出不同的行为特征. 比如. class Program { //下面三各类都继承object,但不同类的tostri ...

  10. C#判断输入的是否为数字（int.TryParse）

    了解 TryParse: TryParse静态方法用来将字符串转换成对应类型的数值. 所以int.TryParse()是将字符串转换为int类型的,如果成功返回true,失败返回false. priv ...