Oracle 维护分区表的索引

维护分区表的索引
虽然分区表和分区索引提供了许多好处,但在设计应用程序时就必须考虑到,创建分区表和分区索引对维护产生的影响。根据环境的情况和具体的应用程序设计和数据库设计,维护操作也会有所不同。对于你的具体应用程序,这包括应用程序的DML模式和被插入,更新和删除的数据量。索引的存在会造成DML操作速度减慢。在某些应用程序中,特别是在数据仓库领域,执行分区一级的操作有利于加快应用程序整体处理速度。分区级的操作可能会对索引产生重大影响,这取决于应用程序使用了什么类型的索引。

下面的例子展示了分区级的操作对不同类型索引的影响。每个例子使用一个测试表,其中包含员工数据。此表上有三个索引:一个非分区索引(employees_part_i1),一个本地分区索引(employees_part_li1)和一个全局分区索引(employees_parttest_gi1)。你会看到对表执行分区级别的操作对表内每个索引的实际影响。

注意:如果在分区表任何一个空的分区上执行下列操作,所有相关索引均不受影响。这对各种索引类型都是成立的,不管它们是本地分区,全局分区还是非分区的索引。

SQL> create table employees_part
  2  (
  3  employee_id number(6) not null,
  4  first_name varchar2(20),
  5  last_name varchar2(25) not null,
  6  email varchar2(25) not null,
  7  phone_numbr varchar2(20),
  8  hire_date date not null,
  9  job_id varchar2(10) not null,
 10  salary number(8,2),
 11  commission_pct number(2,2),
 12  manager_id number(6),
 13  department_id number(4),
 14  constraint employees_part_pk primary key(employee_id,hire_date)
 15  )
 16  partition by range(hire_date)
 17  (
 18  partition p1990 values less than(to_date('1991-01-01','yyyy-mm-dd')),
 19  partition p1991 values less than(to_date('1992-01-01','yyyy-mm-dd')),
 20  partition p1992 values less than(to_date('1993-01-01','yyyy-mm-dd')),
 21  partition p1993 values less than(to_date('1994-01-01','yyyy-mm-dd')),
 22  partition p1994 values less than(to_date('1995-01-01','yyyy-mm-dd')),
 23  partition p1995 values less than(to_date('1996-01-01','yyyy-mm-dd')),
 24  partition p1996 values less than(to_date('1997-01-01','yyyy-mm-dd')),
 25  partition p1997 values less than(to_date('1998-01-01','yyyy-mm-dd')),
 26  partition p1998 values less than(to_date('1999-01-01','yyyy-mm-dd')),
 27  partition p1999 values less than(to_date('2000-01-01','yyyy-mm-dd')),
 28  partition p2000 values less than(to_date('2001-01-01','yyyy-mm-dd')),
 29  partition pmax values less than(maxvalue)
 30  );

Table created.

SQL> create index employee_part_li on employees_part(hire_date) local;

Index created.

SQL> select partition_name,status from user_ind_partitions where index_name='EMPLOYEE_PART_LI';

PARTITION_NAME                                                                                                                   STATUS
-------------------------------------------------------------------------------------------------------------------------------- --------
P1990                                                                                                                            USABLE
P1991                                                                                                                            USABLE
P1992                                                                                                                            USABLE
P1993                                                                                                                            USABLE
P1994                                                                                                                            USABLE
P1995                                                                                                                            USABLE
P1996                                                                                                                            USABLE
P1997                                                                                                                            USABLE
P1998                                                                                                                            USABLE
P1999                                                                                                                            USABLE
P2000                                                                                                                            USABLE
PMAX                                                                                                                             USABLE

12 rows selected.

1 添加分区
往表中添加分区对表上现有的索引影响最小。事实上,无论你选择使用什么索引类型(本地分区,全局分区或非分区),在添加分区操作后,任何现存的索引分区都不会受到影响,也不需要特定的索引级别的操作。下面的例子向测试员工表中添加一个分区,用于保存2001年的历史数据:

SQL> alter table employees_part add partition p2001 values less than(to_date('2002-01-01','yyyy-mm-dd'));
alter table employees_part add partition p2001 values less than(to_date('2002-01-01','yyyy-mm-dd'))
                                         *
ERROR at line 1:
ORA-14074: partition bound must collate higher than that of the last partition


SQL> alter table employees_part drop partition pmax;

Table altered.

SQL> select partition_name,status from user_ind_partitions where index_name='EMPLOYEE_PART_LI';

PARTITION_NAME                                                                                                                   STATUS
-------------------------------------------------------------------------------------------------------------------------------- --------
P1990                                                                                                                            USABLE
P1991                                                                                                                            USABLE
P1992                                                                                                                            USABLE
P1993                                                                                                                            USABLE
P1994                                                                                                                            USABLE
P1995                                                                                                                            USABLE
P1996                                                                                                                            USABLE
P1997                                                                                                                            USABLE
P1998                                                                                                                            USABLE
P1999                                                                                                                            USABLE
P2000                                                                                                                            USABLE

11 rows selected.

SQL> alter table employees_part add partition p2001 values less than(to_date('2002-01-01','yyyy-mm-dd'));

Table altered.

添加分区后,可以运行以下查询来确实添加分区(add partition)操作对表上现有索引的影响:

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       VALID
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    USABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE

13 rows selected.

2 截断分区
截断分区是删除一个表分区内所有数据的最简单的方法。而且,对于创建了本地分区索引的表,截断表分区不影响底层的索引分区,其中包括被截断的分区。然而,如果你的表上有非分区索引或者全局分区索引,截断分区就会使得Oracle无法知道哪些索引条目受到了截断操作的影响。因此,Oracle别无选择,只能简单地把整个索引标记为unusable。例如:

SQL> create index employees_part_uk1 on employees_part(manager_id)
  2  global
  3  partition by range(manager_id)
  4  (
  5  partition manager_100 values less than(100),
  6  partition manager_200 values less than(200),
  7  partition manager_300 values less than(300),
  8  partition manager_400 values less than(400),
  9  partition manager_500 values less than(500),
 10  partition manager_600 values less than(600),
 11  partition manager_700 values less than(700),
 12  partition manager_800 values less than(800),
 13  partition manager_900 values less than(900),
 14  partition manager_max values less than(maxvalue)
 15  );

Index created.

SQL> alter table employees_part truncate partition p1995;

Table truncated.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       VALID
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    USABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE

23 rows selected.

3 移动分区
移动分区有各种原因。你可能需要将一些表或分区移动到不同的表空间,也可能会决定压缩某个分区的数据,或者可能因为大量的更新操作已经导致了行迁移而需要重组表的分区。

执行移动分区操作时,你会再次看到本地分区索引受到的影响是最小的。本地分区索引的分区级移动操作与截断操作的一个关键的区别在于,被移动分区的索引已被标记为unusable。因为移动分区中的每一行后,现在每一行的rowid值都与先前的不同,所以Oracle需要这么做,因此该索引分区的条目现在是无效的,因为它们现在包含过时的rowid项。被移动的索引分区需要重建,以反映新的rowid值。

与截断分区的例子一样,Oracle不了解该表上的全局分区和非分区索引的表分区边界,因此需要把整个索引标志为unusable,且整个索引都需要重建安。对于本地分区索引,只需要重建受移动的表分区影响的索引分区。

在下面的例子中,需要把较旧的1995年的员工数据移动到它自己的表空间,这可能是为了能把它设置成只读:

SQL> alter table employees_part move partition p1995 tablespace reporting_index;

Table altered.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       VALID
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    UNUSABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE

23 rows selected.

4 拆分分区
拆分分区表的分区,通常是因为它不再符合应用程序的要求,或出于维护的原因需要拆分。最常见的原因之一是,需要简单地往表中添加一个分区,而它不是表最高端的分区,正因为如此,这需要通过拆分分区,而不是添加分区来实现。

下面的例子拆分了maxvalue分区以便为早于2003年1月的数据添加一个分区。对于本地分区索引,因为拆分操作触动了pmax分区,并创建一个新的分区(p2002),pmax分区中的行已经被拆分到两个分区中。因为一些数据可能从pmax表分区移动到新的p2002表分区,所以pmax分区的索引项是过时的。因此,在此拆分操作的情况下,这两个本地索引分区都被标记为unusable。由于新的分区以前不存在,其实没有现有的本地索引分区与它对应,所以Oracle自动创建一个索引分区,并把它标记为unusable。

与前面提到的截断和移动操作一样,拆分分区后,所有的全局分区和非分区索引全部被标记为unusable。

SQL> alter table employees_part add partition pmax values less than(maxvalue);

Table altered.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       VALID
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    UNUSABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               PMAX                                     UNUSABLE

24 rows selected.



SQL> alter table employees_part split partition pmax at (to_date('2003-01-01','yyyy-mm-dd')) into
  2  (partition p2002 tablespace reporting_index,partition pmax tablespace reporting_index);

Table altered.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       VALID
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    UNUSABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               P2002                                    UNUSABLE
EMPLOYEE_PART_LI               PMAX                                     UNUSABLE

25 rows selected.
< ?pre>
要强调的重要注意事项是,如果某个实质上往表中添加分区的分区拆分操作是必要的,因为需要一个高端分区来保存某种形式的默认数据,即使只是添加一个空分区的分区拆分操作,也可能会花费相当多的时间。因为Oracle需要分析现有的分区中的每一行,以便有效地执行正确的拆分。在这种情况下,对于指定用maxvalue指定了高端值的表,在高端分区以下,添加一个未被使用且始终为空的“虚拟”分区可能是有益的。那么,如果添加历史分区到表中,你可以始使用空的“虚拟”分区来拆分分区。这提供了两个关键的好处:首先,分区拆分操作会很快,因为没有需要分析的数据;其次,也没有索引将被标记为不可用,因为被拆分的分区没有数据,而新的分区也没有数据。

查看下面的创建表的DDL语句。对于employees_part表,员工离开了公司以后,他们的记录中的hire_date列被修改为maxvalue并留在表中作为历史记录。在这种情况下,pmax分区中将永远有数据。当你在表的pmax分区上执行分区拆分以添加今后几年的分区时,这么做总是会花时间的,而底层索引分区将标记为unusable。通过把p9999分区创建为“虚拟”分区,你绝不会把任何行添加到这个分区中。那么,当你拆分p9999分区来添加2001年及以后年份的数据分区时,它始终是在一个空的分区上进行拆分。因为拆分操作发生在空的分区上面,所以拆分操作将很快完成,而所有底层的本地索引分区将继续可用。
create table employees_part
(
employee_id number(6) not null,
first_name varchar2(20),
last_name varchar2(25) not null,
email varchar2(25) not null,
phone_numbr varchar2(20),
hire_date date not null,
job_id varchar2(10) not null,
salary number(8,2),
commission_pct number(2,2),
manager_id number(6),
department_id number(4),
constraint employees_part_pk primary key(employee_id,hire_date)
)
partition by range(hire_date)
(
partition p1990 values less than(to_date('1991-01-01','yyyy-mm-dd')),
partition p1991 values less than(to_date('1992-01-01','yyyy-mm-dd')),
partition p1992 values less than(to_date('1993-01-01','yyyy-mm-dd')),
partition p1993 values less than(to_date('1994-01-01','yyyy-mm-dd')),
partition p1994 values less than(to_date('1995-01-01','yyyy-mm-dd')),
partition p1995 values less than(to_date('1996-01-01','yyyy-mm-dd')),
partition p1996 values less than(to_date('1997-01-01','yyyy-mm-dd')),
partition p1997 values less than(to_date('1998-01-01','yyyy-mm-dd')),
partition p1998 values less than(to_date('1999-01-01','yyyy-mm-dd')),
partition p1999 values less than(to_date('2000-01-01','yyyy-mm-dd')),
partition p2000 values less than(to_date('2001-01-01','yyyy-mm-dd')),
partition p9999 values less than(to_date('9999-12-31','yyyy-mm-dd')),
partition pmax values less than(maxvalue)
);

5 交换分区
在数据仓库环境中,交换分区进行大批量数据加载特别常见。因为数据被加载到一个独立的表中,所以在加载操作期间读取操作不会受到影响。然后做一个分区交换,这实质上是对数据字典的修改,把一个独立的表段重新指向一个分区表的一部分,并把相关受影响的(原)表分区指向一个独立的表段。

分区交换与分区移动是类似的,只有受影响的本地分区索引的交换分区被标记为unusable。对于全局分区和非分区索引,你可以看到整个索引都已被标记为unusable。

SQL> alter table employees_part exchange partition p1995 with table employees_part_exch;

Table altered.


SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    UNUSABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               P2002                                    USABLE
EMPLOYEE_PART_LI               PMAX                                     USABLE

25 rows selected.

6 删除分区
删除分区,通常发生在基于日期或时间戳的分区表中,因为有些数据已经过期,数据库不再需要这些数据了。对于本地分区索引,删除某个分区对其余的本地索引分区没有任何影响。所有本地分区索引保持在可用(usable)状态。然而,对于全局范围内分区和非分区索引,将再次把整个索引标记为不可用,因为Oracle无法确定这些索引中的哪些行已通过删除分区操作被删除了。

SQL> alter table employees_part drop partition p1995;

Table altered.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               P2002                                    USABLE
EMPLOYEE_PART_LI               PMAX                                     USABLE

24 rows selected.

7 合并分区
合并分区操作本质上是分区拆分的逆操作,正如分区拆分操作,执行分区合并也是为了满足某些应用程序要求或是由于维护的原因。

下面的例子将把p2002和pmax分区全并成一个pmax分区。在这种情况下,两个分区中的所有行实质上被合并到一个新的分区。对于本地分区索引,它有一个匹配pmax的索引分区。因为分区合并改变了分区中行的组成,本地分区索引的pmax分区已被标记为unusable.

因为全局分区索引和非分区索引没有表分区组成的信息,所以整个索引又被标记为unusable.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    USABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               P2002                                    USABLE
EMPLOYEE_PART_LI               PMAX                                     USABLE

25 rows selected.


SQL> alter table employees_part merge partitions p2002,pmax into partition pmax;

Table altered.

SQL> select index_name,null partition_name,status from user_indexes where table_name='EMPLOYEES_PART' and partitioned='NO'
  2  union
  3  select index_name,partition_name,status from user_ind_partitions where index_name in
  4  (select index_name from user_indexes where table_name='EMPLOYEES_PART')
  5  order by 1,2,3;

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEES_PART_PK                                                       UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_100                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_200                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_300                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_400                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_500                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_600                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_700                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_800                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_900                              UNUSABLE
EMPLOYEES_PART_UK1             MANAGER_MAX                              UNUSABLE

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEE_PART_LI               P1990                                    USABLE
EMPLOYEE_PART_LI               P1991                                    USABLE
EMPLOYEE_PART_LI               P1992                                    USABLE
EMPLOYEE_PART_LI               P1993                                    USABLE
EMPLOYEE_PART_LI               P1994                                    USABLE
EMPLOYEE_PART_LI               P1995                                    USABLE
EMPLOYEE_PART_LI               P1996                                    USABLE
EMPLOYEE_PART_LI               P1997                                    USABLE
EMPLOYEE_PART_LI               P1998                                    USABLE
EMPLOYEE_PART_LI               P1999                                    USABLE
EMPLOYEE_PART_LI               P2000                                    USABLE

INDEX_NAME                     PARTITION_NAME                           STATUS
------------------------------ ---------------------------------------- --------
EMPLOYEE_PART_LI               P2001                                    USABLE
EMPLOYEE_PART_LI               PMAX                                     UNUSABLE

24 rows selected.

注意:对于表的大多数分区级操作,如果受影响的分区是空的,那么这种操作不会影响任何相关的索引。

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