码迷,mamicode.com
首页 > 数据库 > 详细

Oracle 分区表的统计信息实例

时间:2015-04-17 18:08:48      阅读:267      评论:0      收藏:0      [点我收藏+]

标签:

  ORACLE的统计信息在执行SQL的过程中扮演着非常重要的作用,而且ORACLE在表的各个层次都会有不同的统计信息,通过这些统计信息来描述表的,列的各种各样的统计信息。下面通过一个复合分区表来说明一些常见的和不常见的统计信息。

搭建测试用例

--创建表。
SQL>
create table test
partition by range(object_id)
subpartition by hash(object_type) subpartitions 4
(partition p1 values less than(10000),
partition p2 values less than(20000),
partition p3 values less than(30000),
partition p4 values less than(maxvalue))
as
select * from dba_objects;

--收集统计信息
sql>
BEGIN
dbms_stats.gather_table_stats(  ownname          => NC60,
                                tabname          => TEST,
                                estimate_percent => 100,                       --百分之百采样
                                block_sample     => FALSE,
                                method_opt       => FOR ALL COLUMNS SIZE 10, --收集直方图
                                granularity      => ALL,                     --所有分区
                                cascade          => TRUE                       --收集索引
                             );
END;

1,表级的统计信息

SQL> select table_name,num_rows,blocks,empty_blocks,avg_space 
  2  from user_tables 
  3  where table_name = TEST;

TABLE_NAME                       NUM_ROWS     BLOCKS EMPTY_BLOCKS  AVG_SPACE
------------------------------ ---------- ---------- ------------ ----------
TEST                                87556       1328            0          0

2,表上列的统计信息

SQL> select table_name,column_name,num_distinct,density 
  2  from user_tab_columns 
  3  where table_name = TEST;

TABLE_NAME                     COLUMN_NAME                    NUM_DISTINCT    DENSITY
------------------------------ ------------------------------ ------------ ----------
TEST                           OWNER                                    34 .023504483
TEST                           OBJECT_NAME                           57495 .000020431
TEST                           SUBOBJECT_NAME                          163 .007094837
TEST                           OBJECT_ID                             87556 .000011421
TEST                           DATA_OBJECT_ID                        22685 .000044786
TEST                           OBJECT_TYPE                              45 .086650298
TEST                           CREATED                                2057 .000847961
TEST                           LAST_DDL_TIME                          1898 .000919514
TEST                           TIMESTAMP                              2182 .000838526
TEST                           STATUS                                    1 5.7106E-06
TEST                           TEMPORARY                                 2 5.7106E-06

TABLE_NAME                     COLUMN_NAME                    NUM_DISTINCT    DENSITY
------------------------------ ------------------------------ ------------ ----------
TEST                           GENERATED                                 2 5.7106E-06
TEST                           SECONDARY                                 2 5.7106E-06
TEST                           NAMESPACE                                21 .116972867
TEST                           EDITION_NAME                              0          0

3,表上列的直方图信息(OBJECT_ID列)

SQL> col TABLE_NAME format a20
SQL> col COLUMN_NAME format a40
SQL> select table_name,column_name,endpoint_number,endpoint_value
  2  from user_tab_histograms
  3  where table_name = TEST
  4  and column_name = OBJECT_ID;

TABLE_NAME           COLUMN_NAME                              ENDPOINT_NUMBER ENDPOINT_VALUE
-------------------- ---------------------------------------- --------------- --------------
TEST                 OBJECT_ID                                              0              2
TEST                 OBJECT_ID                                              1           8921
TEST                 OBJECT_ID                                              2          17998
TEST                 OBJECT_ID                                              3          26754
TEST                 OBJECT_ID                                              4          35510
TEST                 OBJECT_ID                                              5          44266
TEST                 OBJECT_ID                                              6          53025
TEST                 OBJECT_ID                                              7          62172
TEST                 OBJECT_ID                                              8          71290
TEST                 OBJECT_ID                                              9          82232
TEST                 OBJECT_ID                                             10          91577

4,分区的统计信息

SQL> select partition_name,num_rows,blocks,empty_blocks,avg_space
  2  from user_tab_partitions
  3  where table_name = TEST;

PARTITION_NAME                   NUM_ROWS     BLOCKS EMPTY_BLOCKS  AVG_SPACE
------------------------------ ---------- ---------- ------------ ----------
P1                                   9708        147            0          0
P2                                   9805        162            0          0
P3                                  10000        156            0          0
P4                                  58043        863            0          0

5,分区上列的统计信息

SQL> select column_name,num_distinct,density,num_nulls
  2  from user_part_col_statistics
  3  where table_name = TEST
  4  and partition_name = P1;

COLUMN_NAME                              NUM_DISTINCT    DENSITY  NUM_NULLS
---------------------------------------- ------------ ---------- ----------
OWNER                                               5 .000051504          0
OBJECT_NAME                                      7878 .000142267          0
SUBOBJECT_NAME                                     25  .00877193       9594
OBJECT_ID                                        9708 .000103008          0
DATA_OBJECT_ID                                   2074 .000560776       7597
OBJECT_TYPE                                        20 .080003882          0
CREATED                                           141 .011559584          0
LAST_DDL_TIME                                     213 .010730067          0
TIMESTAMP                                         182 .011371733          0
STATUS                                              1 .000051504          0
TEMPORARY                                           2 .000051504          0

COLUMN_NAME                              NUM_DISTINCT    DENSITY  NUM_NULLS
---------------------------------------- ------------ ---------- ----------
GENERATED                                           2 .000051504          0
SECONDARY                                           1 .000051504          0
NAMESPACE                                           8 .000051504          0
EDITION_NAME                                        0          0       9708

6,分区上列的直方图信息(OBJECT_ID列)

SQL> select column_name,bucket_number,endpoint_value
  2  from user_part_histograms
  3  where table_name = TEST
  4  and partition_name = P1
  5  and column_name = OBJECT_ID;

COLUMN_NAME                              BUCKET_NUMBER ENDPOINT_VALUE
---------------------------------------- ------------- --------------
OBJECT_ID                                            0              2
OBJECT_ID                                            1           1030
OBJECT_ID                                            2           2010
OBJECT_ID                                            3           2981
OBJECT_ID                                            4           3952
OBJECT_ID                                            5           4923
OBJECT_ID                                            6           5928
OBJECT_ID                                            7           6953
OBJECT_ID                                            8           7933
OBJECT_ID                                            9           8903
OBJECT_ID                                           10           9999

11 rows selected.

7,子分区的统计信息

SQL> select subpartition_name,num_rows,blocks,empty_blocks
  2  from user_tab_subpartitions
  3  where table_name = TEST
  4  and partition_name = P1;

SUBPARTITION_NAME                NUM_ROWS     BLOCKS EMPTY_BLOCKS
------------------------------ ---------- ---------- ------------
SYS_SUBP21                           3314         48            0
SYS_SUBP22                           3824         57            0
SYS_SUBP23                            528         11            0
SYS_SUBP24                           2042         31            0

SQL>

8,子分区上的列的统计信息

SQL> select column_name,num_distinct,density
  2  from user_subpart_col_statistics
  3  where table_name = TEST
  4  and subpartition_name = SYS_SUBP21;

COLUMN_NAME                              NUM_DISTINCT    DENSITY
---------------------------------------- ------------ ----------
OWNER                                               3 .000150875
OBJECT_NAME                                      3314  .00030175
SUBOBJECT_NAME                                      1 .009615385
OBJECT_ID                                        3314  .00030175
DATA_OBJECT_ID                                    178 .005617978
OBJECT_TYPE                                         7 .000150875
CREATED                                           126 .017527186
LAST_DDL_TIME                                     148  .01653325
TIMESTAMP                                         134 .017483116
STATUS                                              1 .000150875
TEMPORARY                                           2 .000150875

COLUMN_NAME                              NUM_DISTINCT    DENSITY
---------------------------------------- ------------ ----------
GENERATED                                           2 .000150875
SECONDARY                                           1 .000150875
NAMESPACE                                           5 .000150875
EDITION_NAME                                        0          0

9,子分区上的列的直方图信息

SQL> select column_name,bucket_number,endpoint_value
  2  from user_subpart_histograms
  3  where table_name = TEST
  4  and subpartition_name = SYS_SUBP21
  5  and column_name = OBJECT_ID;

COLUMN_NAME                              BUCKET_NUMBER ENDPOINT_VALUE
---------------------------------------- ------------- --------------
OBJECT_ID                                            0            100
OBJECT_ID                                            1           1764
OBJECT_ID                                            2           2429
OBJECT_ID                                            3           3088
OBJECT_ID                                            4           3752
OBJECT_ID                                            5           4309
OBJECT_ID                                            6           4640
OBJECT_ID                                            7           5828
OBJECT_ID                                            8           7278
OBJECT_ID                                            9           8912
OBJECT_ID                                           10           9998

我们对这个复合分区分析之后产生了上面这九种不同层次的统计信息。CBO想要得要一个高效的执行计划需要如此多的统计信息

 

Oracle 分区表的统计信息实例

标签:

原文地址:http://www.cnblogs.com/polestar/p/4435347.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!