ITPub博客

首页 > Linux操作系统 > Linux操作系统 > 分区表

分区表

原创 Linux操作系统 作者:victor1010 时间:2009-05-19 13:31:18 0 删除 编辑

分区表
 

将已存在数据的普通表转变为分区表,没有办法通过修改属性的方式直接转化为分区表,必须通过重建的方式进行转变,一般可以有三种方法,视不同场景使用:

用例:

方法一:利用原表重建分区表。

CREATE TABLE T (ID NUMBER PRIMARY KEY, TIME DATE);
INSERT INTO T
SELECT ROWNUM, SYSDATE - ROWNUM FROM DBA_OBJECTS WHERE ROWNUM <= 5000;
COMMIT;

CREATE TABLE T_NEW (ID, TIME) PARTITION BY RANGE (TIME)
(PARTITION P1 VALUES LESS THAN (TO_DATE('2000-1-1', 'YYYY-MM-DD')),
PARTITION P2 VALUES LESS THAN (TO_DATE('2002-1-1', 'YYYY-MM-DD')),
PARTITION P3 VALUES LESS THAN (TO_DATE('2005-1-1', 'YYYY-MM-DD')),
PARTITION P4 VALUES LESS THAN (MAXVALUE))
AS SELECT ID, TIME FROM T;

 

RENAME T TO T_OLD;

RENAME T_NEW TO T;

SELECT COUNT(*) FROM T;

COUNT(*)
----------
5000

SELECT COUNT(*) FROM T PARTITION (P1);

COUNT(*)
----------
2946

SELECT COUNT(*) FROM T PARTITION (P2);

COUNT(*)
----------
731

SELECT COUNT(*) FROM T PARTITION (P3);

COUNT(*)
----------
1096

优点:方法简单易用,由于采用DDL语句,不会产生UNDO,且只产生少量REDO,效率相对较高,而且建表完成后数据已经在分布到各个分区中了。

不足:对于数据的一致性方面还需要额外的考虑。由于几乎没有办法通过手工锁定T表的方式保证一致性,在执行CREATE TABLE语句和RENAME T_NEW TO T语句直接的修改可能会丢

失,如果要保证一致性,需要在执行完语句后对数据进行检查,而这个代价是比较大的。另外在执行两个RENAME语句之间执行的对T的访问会失败。

适用于修改不频繁的表,在闲时进行操作,表的数据量不宜太大。

 

方法二:使用交换分区的方法。

Drop table t;

CREATE TABLE T (ID NUMBER PRIMARY KEY, TIME DATE);

INSERT INTO T
SELECT ROWNUM, SYSDATE - ROWNUM FROM DBA_OBJECTS WHERE ROWNUM <= 5000;

COMMIT;

CREATE TABLE T_NEW (ID NUMBER PRIMARY KEY, TIME DATE)
PARTITION BY RANGE (TIME)
(
 PARTITION P1 VALUES LESS THAN (TO_DATE('2005-9-1', 'YYYY-MM-DD')),
 PARTITION P2 VALUES LESS THAN (MAXVALUE)
);

 

ALTER TABLE T_NEW EXCHANGE PARTITION P1 WITH TABLE T;

RENAME T TO T_OLD;

RENAME T_NEW TO T;

 

优点:只是对数据字典中分区和表的定义进行了修改,没有数据的修改或复制,效率最高。如果对数据在分区中的分布没有进一步要求的话,实现比较简单。在执行完RENAME操作

后,可以检查T_OLD中是否存在数据,如果存在的话,直接将这些数据插入到T中,可以保证对T插入的操作不会丢失。

不足:仍然存在一致性问题,交换分区之后RENAME T_NEW TO T之前,查询、更新和删除会出现错误或访问不到数据。如果要求数据分布到多个分区中,则需要进行分区的SPLIT操

作,会增加操作的复杂度,效率也会降低。

适用于包含大数据量的表转到分区表中的一个分区的操作。应尽量在闲时进行操作。

 
分区管理:

增加分区:
alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD'));

如果已有maxvalue分区,不能增加分区,可以采取分裂分区的办法增加分区!
tstuser@RMIS> alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1
', 'YYYY-MM-DD'));
alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD
'))
                            *
ERROR at line 1:
ORA-14074: partition bound must collate higher than that of the last partition

分裂分区:
alter table t split partition p4 at (TO_DATE('2007-1-1', 'YYYY-MM-DD')) into (partition p4,partition p5);

查看分区信息:
select  a.table_name,a.partitioning_type,a.partition_count,a.partitioning_key_count from user_part_tables a ;
select a.table_name,a.partition_name,a.high_value  from user_tab_partitions a where a.table_name='T';

截短分区:
alter table T truncate partition P5;

合并分区:

alter table t merge partitions p3, p4 into partition p4;

删除分区:

ALTER TABLE t DROP PARTITION p5;

 

测试过程:

 

tstuser@RMIS> CREATE TABLE T (ID NUMBER PRIMARY KEY, TIME DATE);

Table created.

tstuser@RMIS> INSERT INTO T
  2  SELECT ROWNUM, SYSDATE - ROWNUM FROM DBA_OBJECTS WHERE ROWNUM <= 5000;

5000 rows created.

tstuser@RMIS> COMMIT;

Commit complete.

tstuser@RMIS> CREATE TABLE T_NEW (ID, TIME) PARTITION BY RANGE (TIME)
  2  (PARTITION P1 VALUES LESS THAN (TO_DATE('2000-1-1', 'YYYY-MM-DD')),
  3  PARTITION P2 VALUES LESS THAN (TO_DATE('2002-1-1', 'YYYY-MM-DD')),
  4  PARTITION P3 VALUES LESS THAN (TO_DATE('2005-1-1', 'YYYY-MM-DD')),
  5  PARTITION P4 VALUES LESS THAN (MAXVALUE))
  6  AS SELECT ID, TIME FROM T;

Table created.

tstuser@RMIS> RENAME T TO T_OLD;
RENAME T TO T_OLD
            *
ERROR at line 1:
ORA-00955: name is already used by an existing object


tstuser@RMIS> drop table t_old;

Table dropped.

tstuser@RMIS> RENAME T TO T_OLD;

Table renamed.

tstuser@RMIS> RENAME T_NEW TO T;

Table renamed.

tstuser@RMIS> SELECT COUNT(*) FROM T;

  COUNT(*)
----------
      5000

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P1);

  COUNT(*)
----------
      1574

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P2);

  COUNT(*)
----------
       731

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P3);

  COUNT(*)
----------
      1096

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P4);

  COUNT(*)
----------
      1599

tstuser@RMIS> alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD'));
alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD'))
                            *
ERROR at line 1:
ORA-14074: partition bound must collate higher than that of the last partition


tstuser@RMIS> select  a.table_name,a.partitioning_type,a.partition_count,a.partitioning_key_count from user_part_tables a ;

TABLE_NAME                                                   PARTITIONING_T PARTITION_COUNT PARTITIONING_KEY_COUNT
------------------------------------------------------------ -------------- --------------- ----------------------
T                                                            RANGE                        4                      1
TEST_PARTION                                                 RANGE                        5                      1

tstuser@RMIS> select a.table_name,a.partition_name,a.high_value  from user_tab_partitions a where a.table_name='T';

TABLE_NAME
------------------------------------------------------------
PARTITION_NAME
------------------------------------------------------------
HIGH_VALUE
--------------------------------------------------------------------------------
T
P1
TO_DATE(' 2000-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
N')

T
P2
TO_DATE(' 2002-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
N')

T
P3
TO_DATE(' 2005-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA
N')

T
P4
MAXVALUE


tstuser@RMIS> alter table t split partition p4 at (TO_DATE('2007-1-1', 'YYYY-MM-DD')) into (partition p4,partition p5);

Table altered.

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P4);

  COUNT(*)
----------
       730

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P5);

  COUNT(*)
----------
       869

tstuser@RMIS> alter table T truncate partition P5;

Table truncated.

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P5);

  COUNT(*)
----------
         0

tstuser@RMIS> alter table t merge partitions p3, p4 into partition p4;

Table altered.

tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P3);
SELECT COUNT(*) FROM T PARTITION (P3)
                                  *
ERROR at line 1:
ORA-02149: Specified partition does not exist


tstuser@RMIS> SELECT COUNT(*) FROM T PARTITION (P4);

  COUNT(*)
----------
      1826

tstuser@RMIS> ALTER TABLE t DROP PARTITION p5;

Table altered.

tstuser@RMIS> alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD'));
alter table t add partition P5 VALUES LESS THAN (TO_DATE('2007-1-1', 'YYYY-MM-DD'))
                            *
ERROR at line 1:
ORA-14074: partition bound must collate higher than that of the last partition


tstuser@RMIS> alter table t add partition P5 VALUES LESS THAN (TO_DATE('2008-1-1', 'YYYY-MM-DD'));

Table altered.

tstuser@RMIS> spool off;

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/8102208/viewspace-600421/,如需转载,请注明出处,否则将追究法律责任。

请登录后发表评论 登录
全部评论

注册时间:2008-04-29

  • 博文量
    296
  • 访问量
    565801