浅谈Oracle分区表之范围分区

在oracle 10g世界里面，分区表主要分range,hash,list,range-hash,range-list五种类型，在oracle 11g中，则发展到了3*3的分区组合类型，以满足更多的应用场景！但无论在什么情况下，范围分区都是最常见的一种表分区方式，尤其在需要对过期的数据进行整理归档，只保留一定时期内的数据的条件下，几乎都会优先选择使用范围分区的方式！分区表可以说是一项百利而无一害的技术，当数据量达到一定的级别后(通常是超过100G后)，就算使用了ASM技术，数据库中一样会产生严重的I/O等待事件！

下面来简要介绍下范围分区，范围分区的主要优点主要如下：

1：分区表可以将表存储在多个表空间内，进而离散I/O；

2：同时各个分区维护各自的本地索引(一般使用local索引，而不是global索引)；

3：select语句可以根据索引进行分区范围扫描，减少查询语句所带来的一致性读；

4：可以对单个分区进行备份或者truncate，归档或者清除过期的数据；

5: 可以方便的对表的分区进行添加，删除，truncate，拆分和合并操作

一：创建一张分区表，分区的条件是以销售日期来界定，同时分区的索引为本地索引，每个分区的对应一个单独的表空间，基于离散I/O和方便管理的双重需要

SQL> create table sale_data 2 (sale_id number(5), salesman_name varchar2(30),sales_date date) 3 partition by range(sales_date) 4 ( 5 partition sales_01 values less than (to_date('01/02/2012','DD/MM/YYYY')) tablespace tbs_sale01, 6 partition sales_02 values less than (to_date('01/03/2012','DD/MM/YYYY')) tablespace tbs_sale02, 7 partition sales_03 values less than (to_date('01/04/2012','DD/MM/YYYY')) tablespace tbs_sale03, 8 partition sales_04 values less than (to_date('01/05/2012','DD/MM/YYYY')) tablespace tbs_sale04, 9 partition sales_05 values less than (to_date('01/06/2012','DD/MM/YYYY')) tablespace tbs_sale05, 10 partition sales_06 values less than (to_date('01/07/2012','DD/MM/YYYY')) tablespace tbs_sale06, 11 partition sales_07 values less than (to_date('01/08/2012','DD/MM/YYYY')) tablespace tbs_sale07, 12 partition sales_08 values less than (to_date('01/09/2012','DD/MM/YYYY')) tablespace tbs_sale08, 13 partition sales_09 values less than (to_date('01/10/2012','DD/MM/YYYY')) tablespace tbs_sale09, 14 partition sales_10 values less than (to_date('01/11/2012','DD/MM/YYYY')) tablespace tbs_sale10, 15 partition sales_11 values less than (to_date('01/12/2012','DD/MM/YYYY')) tablespace tbs_sale11, 16* partition sales_12 values less than (to_date('31/12/2012','DD/MM/YYYY')) tablespace tbs_sale12) Table created. SQL> select owner,partitioning_type,partition_count,status from dba_part_tables where table_name='SALE_DATE'; OWNER PARTITI PARTITION_COUNT STATUS ------------------------------ ------- --------------- -------- SALE RANGE 12 VALID SQL> create index ind_sale_data_date on sale_data(sale_id) local 2 ( 3 partition sales_01 tablespace tbs_sale01, 4 partition sales_02 tablespace tbs_sale02, 5 partition sales_03 tablespace tbs_sale03, 6 partition sales_04 tablespace tbs_sale04, 7 partition sales_05 tablespace tbs_sale05, 8 partition sales_06 tablespace tbs_sale06, 9 partition sales_07 tablespace tbs_sale07, 10 partition sales_08 tablespace tbs_sale08, 11 partition sales_09 tablespace tbs_sale09, 12 partition sales_10 tablespace tbs_sale10, 13 partition sales_11 tablespace tbs_sale11, 14* partition sales_12 tablespace tbs_sale12) Index created. SQL> select segment_name,partition_name,tablespace_name from user_segments where segment_name in ('SALE_DATA','IND_SALE_DATA_DATE'); SEGMENT_NAME PARTITION_NAME TABLESPACE_NAME -------------------- ------------------------------ -------------------- SALE_DATA SALES_01 TBS_SALE01 SALE_DATA SALES_02 TBS_SALE02 SALE_DATA SALES_03 TBS_SALE03 SALE_DATA SALES_04 TBS_SALE04 SALE_DATA SALES_05 TBS_SALE05 SALE_DATA SALES_06 TBS_SALE06 SALE_DATA SALES_07 TBS_SALE07 SALE_DATA SALES_08 TBS_SALE08 SALE_DATA SALES_09 TBS_SALE09 SALE_DATA SALES_10 TBS_SALE10 SALE_DATA SALES_11 TBS_SALE11 SEGMENT_NAME PARTITION_NAME TABLESPACE_NAME -------------------- ------------------------------ -------------------- SALE_DATA SALES_12 TBS_SALE12 IND_SALE_DATA_DATE SALES_01 TBS_SALE01 IND_SALE_DATA_DATE SALES_02 TBS_SALE02 IND_SALE_DATA_DATE SALES_03 TBS_SALE03 IND_SALE_DATA_DATE SALES_04 TBS_SALE04 IND_SALE_DATA_DATE SALES_05 TBS_SALE05 IND_SALE_DATA_DATE SALES_06 TBS_SALE06 IND_SALE_DATA_DATE SALES_07 TBS_SALE07 IND_SALE_DATA_DATE SALES_08 TBS_SALE08 IND_SALE_DATA_DATE SALES_09 TBS_SALE09 IND_SALE_DATA_DATE SALES_10 TBS_SALE10 SEGMENT_NAME PARTITION_NAME TABLESPACE_NAME -------------------- ------------------------------ -------------------- IND_SALE_DATA_DATE SALES_11 TBS_SALE11 IND_SALE_DATA_DATE SALES_12 TBS_SALE12

二：插入测试数据，收集优化器的统计信息(包括索引)，当前的系统时间为2012年3月12日(传说中的植树节哦！)，因而数据应当在sales_03和sales_05两个分区

SQL> begin
2  for i in 1..10000
3  loop
4  insert into sale_data values (i,'yang',sysdate);
5  commit;
6  end loop;
7* end;
PL/SQL procedure successfully completed.

SQL> begin
2  for i in 1..10000
3  loop
4  insert into sale_data values (i,'yang',sysdate+60);
5  commit;
6  end loop;
7* end;
PL/SQL procedure successfully completed.

SQL> exec dbms_stats.gather_table_stats('SALE','SALE_DATA',CASCADE => TRUE);
PL/SQL procedure successfully completed.

三：以sys用户运行，将plustrace权限赋予用户sale

SQL> @?/sqlplus/admin/plustrce.sql;
SQL>
SQL> drop role plustrace;
drop role plustrace
*
ERROR at line 1:
ORA-01919: role 'PLUSTRACE' does not exist

SQL> create role plustrace;
Role created.

SQL> grant select on v_$sesstat to plustrace;
Grant succeeded.

SQL> grant select on v_$statname to plustrace;
Grant succeeded.

SQL> grant select on v_$mystat to plustrace;
Grant succeeded.

SQL> grant plustrace to dba with admin option;
Grant succeeded.

SQL> set echo off
SQL> grant plustrace to sale;
Grant succeeded.

四：查看在分区表上的查询语句的执行计划

SQL> set autot trace exp stat SQL> select count(*) from sale_data; Execution Plan ---------------------------------------------------------- Plan hash value: 268098023 ------------------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 1 | 17 (0)| 00:00:01 | | | | 1 | SORT AGGREGATE | | 1 | | | | | | 2 | PARTITION RANGE ALL| | 20000 | 17 (0)| 00:00:01 | 1| 12 | | 3 | TABLE ACCESS FULL | SALE_DATA | 20000 | 17 (0)| 00:00:01 | | 12 | -------------------------------------------------------------------------------- Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 106 consistent gets 0 physical reads 0 redo size 515 bytes sent via SQL*Net to client 469 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed 可以看到，统计整个分区表的行数的时候，先走了全表扫描，而后是全部的分区范围扫描，总共有106个一致性读！ SQL> select count(*) from sale_data partition(sales_03); Execution Plan ---------------------------------------------------------- Plan hash value: 2733649240 -------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Cost (%CPU)| Time | Pstart| Pstop | -------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 9 (0)| 00:00:01 | | | | 1 | SORT AGGREGATE | | 1 | | | | | | 2 | PARTITION RANGE SINGLE| | 10000 | 9 (0)| 00:00:01 | 3 | 3 | | 3 | TABLE ACCESS FULL | SALE_DATA | 10000 | 9 (0)| 00:00:01 |3 | 3 | -------------------------------------------------------------------------------- Statistics ---------------------------------------------------------- 1 recursive calls 0 db block gets 38 consistent gets 0 physical reads 0 redo size 515 bytes sent via SQL*Net to client 469 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed 可以看到，统计整个分区表的行数的时候，先走了全表扫描，而后是单个的分区范围扫描，总共有38个一致性读！ SQL> set autot trace exp stat SQL> select * from sale_data partition(sales_03) where sale_id=100; SALE_ID SALESMAN_NAME SALES_DATE ---------- ------------------------------ ------------------- 100 yang 2012-03-12:20:04:31 Execution Plan ---------------------------------------------------------- Plan hash value: 4229050284 -------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes| Cost (%CPU)| Time | Pstart| Pstop | -------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 16| 2 (0)| 00:00:01 | | | | 1 | PARTITION RANGE SINGLE | | 1 | 16| 2 (0)| 00:00:01 | 3 | 3 | | 2 | TABLE ACCESS BY LOCAL INDEX ROWID| SALE_DATA | 1 | 162| 2 (0)| 00:00:01 | 3 | 3 | |* 3 | INDEX RANGE SCAN | IND_SALE_DATA_DATE | 1 | | 1 (0)| 00:00:01 | 3 | 3 | -------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("SALE_ID"=100) Statistics ---------------------------------------------------------- 1 recursive calls 0 db block gets 4 consistent gets 0 physical reads 0 redo size 666 bytes sent via SQL*Net to client 469 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed 可以看到，当进行等值查询的时候，先走了范围索引扫描，而后是通过本地索引定位rowid，然后访问单个分区，总共有4个一致性读！

五：对单个分区的truncate操作

SQL> select count(*) from sale_data partition(sales_03);

COUNT(*)
----------
10000

SQL> select count(*) from sale_data partition(sales_05);

COUNT(*)
----------
10000

SQL> select * from sale_data partition(sales_03) where rownum=1;

SALE_ID SALESMAN_NAME          SALES_DATE
---------- ------------------------------ -------------------
1 yang               2012-03-12:20:04:31

SQL> select * from sale_data partition(sales_05) where rownum=1;

SALE_ID SALESMAN_NAME          SALES_DATE
---------- ------------------------------ -------------------
1 yang               2012-05-11:20:08:45

SQL> alter table sale_data truncate partition sales_03;
Table truncated.

SQL> select count(*) from sale_data partition(sales_03);

COUNT(*)
----------
0

六：添加分区(非默认)以及默认分区(对应范围分区的最大值)，本地索引会自动创建，删除分区的时候，索引也会自动维护！

SQL> alter table sale_data add partition sales_13 values less than (to_date('01/02/2013','DD/MM/YYYY')) tablespace tbs_sale12;
Table altered.

SQL> alter table sale_data add partition sales_14 values less than (maxvalue) tablespace tbs_sale12;
Table altered.

SQL> select segment_name,partition_name,tablespace_name from user_segments where segment_name='IND_SALE_DATA_DATE' and partition_name in ('SALES_13','SALES_14');

SEGMENT_NAME         PARTITION_NAME   TABLESPACE_NAME
-------------------- -------------------- ------------------------------
IND_SALE_DATA_DATE   SALES_13         TBS_SALE12
IND_SALE_DATA_DATE   SALES_14         TBS_SALE12

SQL> alter table sale_data drop partition sales_13;
Table altered.

SQL> alter table sale_data drop partition sales_14;
Table altered.

SQL> select segment_name,partition_name,tablespace_name from user_segments where segment_name='IND_SALE_DATA_DATE' and partition_name in ('SALES_13','SALES_14');
no rows selected.

七：下面来讨论下表分区的拆分与合并，创建一张结构简单的分区表来说明，根据用户id进行分区；

SQL> create table emp (id number,first_name char(10))
2  partition by range(id)
3  (
4  partition p_1 values less than (10000) tablespace tbs_sale01,
5  partition p_2 values less than (20000) tablespace tbs_sale02,
6* partition p_3 values less than (30000) tablespace tbs_sale03)
Table created.

SQL> begin
2  for i in 1..20000
3  loop
4  insert into emp values (i,'t_i');
5  commit;
6  end loop;
7* end;
PL/SQL procedure successfully completed.

1:首先，当创建分区表的时候未指定maxvalue值所在的分区的情况下，插入分区以外的值，将会报ORA-14400错误

SQL> insert into emp values (30001,'t');
insert into emp values (30001,'t')
*
ERROR at line 1:
ORA-14400: inserted partition key does not map to any partition

SQL> alter table emp add partition p_max values less than (maxvalue) tablespace tbs_sale04;
Table altered.

SQL> insert into emp values (30001,'t');
1 row created.

SQL> commit;
Commit complete.

SQL> select * from emp partition(p_max);

ID FIRST_NAME
---------- ----------
30001 t

2：将p_1分区进行拆分操作

SQL> select partition_name,tablespace_name from user_segments where segment_name='EMP';

PARTITION_NAME             TABLESPACE_NAME
------------------------------ ------------------------------
P_1                TBS_SALE01
P_2                TBS_SALE02
P_3                TBS_SALE03
P_MAX              TBS_SALE04

SQL> alter table emp split partition p_1 at('9999') into (partition p_1_01 tablespace tbs_sale02,partition p_1_02 tablespace tbs_sale03);
Table altered.

SQL> select partition_name,tablespace_name from user_segments where segment_name='EMP';

PARTITION_NAME             TABLESPACE_NAME
------------------------------ ------------------------------
P_2                    TBS_SALE02
P_3                    TBS_SALE03
P_MAX                  TBS_SALE04
P_1_01                 TBS_SALE02
P_1_02                 TBS_SALE03

SQL> select count(*) from emp partition(p_1_01);

COUNT(*)
----------
9998

SQL> select count(*) from emp partition(p_1_02);

COUNT(*)
----------
1
由此可见，at关键字指的是在这个点进行拆分，且包含这个点！

3：将p_1_01和p_1_02分区进行合并操作，若不指定表空间，将使用用户的默认表空间

SQL> alter table emp merge partitions p_1_01,p_1_02 into partition p_01;
Table altered.

SQL> select partition_name,tablespace_name from user_segments where segment_name='EMP';

PARTITION_NAME             TABLESPACE_NAME
------------------------------ ------------------------------
P_01                   USERS
P_2                    TBS_SALE02
P_3                    TBS_SALE03
P_MAX                  TBS_SALE04

八：针对单个分区的导出和导入，使用expdp和impdp实现

1：查看表各个分区的情况，创建目录对象并授权，导出分区P_1

SQL> select PARTITION_NAME ,TABLESPACE_NAME from user_segments where segment_name='EMP';

PARTITION_NAME                 TABLESPACE_NAME
------------------------------ ------------------------------
P_1                            TBS_SALE01
P_2                            TBS_SALE02
P_3                     &nb
20646
sp;      TBS_SALE03
P_MAX                          TBS_SALE04

SQL> select count(*) from emp partition (p_1);

COUNT(*)
----------
9999

SQL> select count(*) from emp partition (p_2);

COUNT(*)
----------
10000

SQL> select count(*) from emp partition (p_3);

COUNT(*)
----------
1

SQL> select count(*) from emp partition (p_max);

COUNT(*)
----------
1

SQL> conn /as sysdba
Connected.

SQL> create directory dir01 as '/home/oracle/dir01';
Directory created.

SQL> grant read,write on directory dir01 to sale;
Grant succeeded.

[oracle@rhel6 ~]$ expdp help=y
Example: expdp scott/tiger DUMPFILE=scott.dmp DIRECTORY=dmpdir SCHEMAS=scott
or TABLES=(T1:P1,T1:P2), if T1 is partitioned table

[oracle@rhel6 ~]$ expdp sale/123456 directory=dir01 dumpfile=emp_p1.dmp logfile=emp_p1.log   tables=emp:p_1
Export: Release 10.2.0.1.0 - 64bit Production on Tuesday, 13 March, 2012 21:06:13
Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
Starting "SALE"."SYS_EXPORT_TABLE_01":  sale/******** directory=dir01 dumpfile=emp_p1.dmp logfile=emp_p1.log tables=emp:p_1
Estimate in progress using BLOCKS method...
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 256 KB
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
. . exported "SALE"."EMP":"P_1"                          190.5 KB    9999 rows
Master table "SALE"."SYS_EXPORT_TABLE_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SALE.SYS_EXPORT_TABLE_01 is:
/home/oracle/dir01/emp_p1.dmp
Job "SALE"."SYS_EXPORT_TABLE_01" successfully completed at 21:06:17

2.导出完成后，截断P_1分区

[oracle@rhel6 ~]$ sqlplus sale/123456
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Mar 13 21:07:18 2012
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> alter table emp truncate partition p_1;
Table truncated.

SQL> select count(*) from emp partition (p_1);

COUNT(*)
----------
0

3：导入分区P_1的备份，需要设置table_exists_action参数为append，否则将导入失败

[oracle@rhel6 ~]$ impdp sale/123456 directory=dir01 dumpfile=emp_p1.dmp logfile=emp_p1.log2  table_exists_action=append tables=emp:p_1
Import: Release 10.2.0.1.0 - 64bit Production on Tuesday, 13 March, 2012 21:29:58
Copyright (c) 2003, 2005, Oracle.  All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
Master table "SALE"."SYS_IMPORT_TABLE_01" successfully loaded/unloaded
Starting "SALE"."SYS_IMPORT_TABLE_01":  sale/******** directory=dir01 dumpfile=emp_p1.dmp logfile=emp_p1.log2 table_exists_action=append tables=emp:p_1
Processing object type TABLE_EXPORT/TABLE/TABLE
ORA-39152: Table "SALE"."EMP" exists. Data will be appended to existing table but all dependent metadata will be skipped due to table_exists_action of append
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "SALE"."EMP":"P_1"                          190.5 KB    9999 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Job "SALE"."SYS_IMPORT_TABLE_01" completed with 1 error(s) at 21:30:01

SQL> conn sale/123456
Connected.
SQL> select count(*) from emp partition (p_1);

COUNT(*)
----------
9999

九：分区交换，这是一项非常实用的技术，即可以将字段完全相同的分区表分区和普通表进行存储空间的交换，从而达到数据交换的目的。就类似于将两个用户的名字对调，而原本用户用户的对象都没有改变。并且，当仅有local分区索引，且和普通表的索引相对应时，还可以将索引一起作交换。exchange partition的语法如下：

ALTER TABLE table1

EXCHANGE PARTITION partition

WITH TABLE table2

[{ INCLUDING | EXCLUDING } INDEXES]

[{ WITH | WITHOUT } VALIDATION]

[EXCEPTIONS INTO [schema.]table]

[UPDATE/NVALIDATE GLOBAL INDEXES

[NOPARALLEL/PARALLEL[int]]]

SQL> create table emp_exchange as select * from emp where 1=0;
Table created.

SQL> select count(*) from emp_exchange;

COUNT(*)
----------
0

SQL> select count(*) from emp partition(p_1);

COUNT(*)
----------
9999

SQL> alter table emp exchange partition p_1 with table emp_exchange;
Table altered.

SQL> select count(*) from emp partition(p_1);

COUNT(*)
----------
0

SQL> select count(*) from emp_exchange;

COUNT(*)
----------
9999

SQL> select tablespace_name from user_segments where segment_name='EMP_EXCHANGE';

TABLESPACE_NAME
------------------------------
TBS_SALE01

SQL> select tablespace_name from user_segments where segment_name='EMP';

TABLESPACE_NAME
------------------------------
USERS
TBS_SALE02
TBS_SALE03
TBS_SALE04