使用DBMS_REDEFINITION在线切换普通表到分区表

      随着数据库数据量的不断增长，有些表须要由普通的堆表转换为分区表的模式。有几种不同的方法来对此进行操作。诸如导出表数据，然后创建分区表再导入数据到分区表；使用EXCHANGE PARTITION方式来转换为分区表以及使用DBMS_REDEFINITION来在线重定义分区表。本文描写叙述的是使用DBMS_REDEFINITION来实现，以下是详细的操作演示样例。

      有关详细的dbms_redefinition在线重定义表的原理及步骤可參考：基于 dbms_redefinition 在线重定义表
      有关分区表的描写叙述请參考：Oracle 分区表

1、准备环境

--创建用户
SQL> create user leshami identified by xxx;

SQL> grant dba to leshami;

--创建演示须要用到的表空间
SQL> create tablespace tbs_tmp datafile '/u02/database/SYBO2/oradata/tbs_tmp.dbf' size 10m autoextend on;

SQL> alter user leshami default tablespace tbs_tmp;

SQL> create tablespace tbs1 datafile '/u02/database/SYBO2/oradata/tbs1.dbf' size 10m autoextend on;

SQL> create tablespace tbs2 datafile '/u02/database/SYBO2/oradata/tbs2.dbf' size 10m autoextend on;

SQL> create tablespace tbs3 datafile '/u02/database/SYBO2/oradata/tbs3.dbf' size 10m autoextend on;

SQL> conn leshami/xxx

-- 创建一个lookup表
CREATE TABLE lookup (
  id            NUMBER(10),
  description   VARCHAR2(50)
);

--加入主键约束
ALTER TABLE lookup ADD (
  CONSTRAINT lookup_pk PRIMARY KEY (id)
);

--插入数据
INSERT INTO lookup (id, description) VALUES (1, 'ONE');
INSERT INTO lookup (id, description) VALUES (2, 'TWO');
INSERT INTO lookup (id, description) VALUES (3, 'THREE');
COMMIT;

--创建一个用于切换到分区的大表
CREATE TABLE big_table (
  id            NUMBER(10),
  created_date  DATE,
  lookup_id     NUMBER(10),
  data          VARCHAR2(50)
);

--填充数据到大表
DECLARE
  l_lookup_id    lookup.id%TYPE;
  l_create_date  DATE;
BEGIN
  FOR i IN 1 .. 1000000 LOOP
    IF MOD(i, 3) = 0 THEN
      l_create_date := ADD_MONTHS(SYSDATE, -24);
      l_lookup_id   := 2;
    ELSIF MOD(i, 2) = 0 THEN
      l_create_date := ADD_MONTHS(SYSDATE, -12);
      l_lookup_id   := 1;
    ELSE
      l_create_date := SYSDATE;
      l_lookup_id   := 3;
    END IF;
    
    INSERT INTO big_table (id, created_date, lookup_id, data)
    VALUES (i, l_create_date, l_lookup_id, 'This is some data for ' || i);
  END LOOP;
  COMMIT;
END;
/

--为大表加入主、外键约束。索引，以及加入触发器等.
ALTER TABLE big_table ADD (
  CONSTRAINT big_table_pk PRIMARY KEY (id)
);

CREATE INDEX bita_created_date_i ON big_table(created_date);

CREATE INDEX bita_look_fk_i ON big_table(lookup_id);

ALTER TABLE big_table ADD (
  CONSTRAINT bita_look_fk
  FOREIGN KEY (lookup_id)
  REFERENCES lookup(id)
);

CREATE OR REPLACE TRIGGER tr_bf_big_table
   BEFORE UPDATE OF created_date
   ON big_table
   FOR EACH ROW
BEGIN
   :new.created_date := TO_CHAR (SYSDATE, 'yyyymmdd hh24:mi:ss');
END tr_bf_big_table;
/

--收集统计信息
EXEC DBMS_STATS.gather_table_stats('LESHAMI', 'LOOKUP', cascade => TRUE);
EXEC DBMS_STATS.gather_table_stats('LESHAMI', 'BIG_TABLE', cascade => TRUE);

--表上的索引相关信息
SQL> @idx_info
TABLE_NAME                INDEX_NAME                     CL_NAM                  STATUS   PAR 
------------------------- ------------------------------ --------------------    -------- --- 
LOOKUP                    LOOKUP_PK                      ID                      VALID    NO  
BIG_TABLE                 BIG_TABLE_PK                   ID                      VALID    NO 
BIG_TABLE                 BITA_CREATED_DATE_I            CREATED_DATE            VALID    NO 
BIG_TABLE                 BITA_LOOK_FK_I                 LOOKUP_ID               VALID    NO

--创建一个中间表(分区表)
CREATE TABLE big_table2 (
  id            NUMBER(10),
  created_date  DATE,
  lookup_id     NUMBER(10),
  data          VARCHAR2(50)
)
PARTITION BY RANGE (created_date)
(PARTITION big_table_2012 VALUES LESS THAN (TO_DATE('01/01/2013', 'DD/MM/YYYY')) tablespace tbs1,
 PARTITION big_table_2013 VALUES LESS THAN (TO_DATE('01/01/2014', 'DD/MM/YYYY')) tablespace tbs2,
 PARTITION big_table_2014 VALUES LESS THAN (MAXVALUE) tablespace tbs3);

2、切换普通表到分区表

----校验表是否能被重定义 
EXEC DBMS_REDEFINITION.CAN_REDEF_TABLE('LESHAMI', 'BIG_TABLE');

--開始重定义
BEGIN
 DBMS_REDEFINITION.start_redef_table(
   uname      => 'LESHAMI',        
   orig_table => 'BIG_TABLE',
   int_table  => 'BIG_TABLE2');
END;
/

--可选步骤，用于同步重定义表与暂时表  
BEGIN
  dbms_redefinition.sync_interim_table(
    uname      => 'LESHAMI',        
    orig_table => 'BIG_TABLE',
    int_table  => 'BIG_TABLE2');
END;
/

--为中间表加入对应的索引。约束等
ALTER TABLE big_table2 ADD (
  CONSTRAINT big_table_pk2 PRIMARY KEY (id)
);

CREATE INDEX bita_created_date_i2 ON big_table2(created_date) LOCAL;

CREATE INDEX bita_look_fk_i2 ON big_table2(lookup_id) LOCAL;

ALTER TABLE big_table2 ADD (
  CONSTRAINT bita_look_fk2
  FOREIGN KEY (lookup_id)
  REFERENCES lookup(id)
);

--为中间表加入触发器
CREATE OR REPLACE TRIGGER tr_bf_big_table2
   BEFORE UPDATE OF created_date
   ON big_table2
   FOR EACH ROW
BEGIN
   :new.created_date := TO_CHAR (SYSDATE, 'yyyymmdd hh24:mi:ss');
END tr_bf_big_table2;
/

-- Gather statistics on the new table.
EXEC DBMS_STATS.gather_table_stats('LESHAMI', 'BIG_TABLE2', cascade => TRUE);

--完毕在线重定义
BEGIN
  dbms_redefinition.finish_redef_table(      --Author : Leshami
    uname      => 'LESHAMI',                 --Blog   : http://blog.csdn.net/leshmai  
    orig_table => 'BIG_TABLE',
    int_table  => 'BIG_TABLE2');
END;
/

--能够看到新的表BIG_TABLE上的索引已经成为分区索引，如最后一列所看到的
SQL> @idx_info

TABLE_NAME                     INDEX_NAME                     CL_NAM                         STATUS   PAR
------------------------------ ------------------------------ ------------------------------ -------- ---
BIG_TABLE                      BIG_TABLE_PK2                  ID                             VALID    NO
BIG_TABLE                      BITA_LOOK_FK_I2                LOOKUP_ID                      N/A      YES
BIG_TABLE                      BITA_CREATED_DATE_I2           CREATED_DATE                   N/A      YES
BIG_TABLE2                     BITA_CREATED_DATE_I            CREATED_DATE                   VALID    NO
BIG_TABLE2                     BIG_TABLE_PK                   ID                             VALID    NO
BIG_TABLE2                     BITA_LOOK_FK_I                 LOOKUP_ID                      VALID    NO
LOOKUP                         LOOKUP_PK                      ID                             VALID    NO

--校验分区表
SQL> select table_name, partition_name,high_value,num_rows from user_tab_partitions where table_name='BIG_TABLE';

TABLE_NAME                PARTITION_NAME                 HIGH_VALUE                        NUM_ROWS
------------------------- ------------------------------ ------------------------------- ----------
BIG_TABLE                 BIG_TABLE_2012                 TO_DATE(' 2013-01-01 00:00:00',     333793
BIG_TABLE                 BIG_TABLE_2013                 TO_DATE(' 2014-01-01 00:00:00',     332025
BIG_TABLE                 BIG_TABLE_2014                 MAXVALUE                            333128

3、切换后的收尾工作

--移除中间表
DROP TABLE big_table2;

--依据须要能够重命名索引及约束名
ALTER TABLE big_table RENAME CONSTRAINT big_table_pk2 TO big_table_pk;
ALTER TABLE big_table RENAME CONSTRAINT bita_look_fk2 TO bita_look_fk;
ALTER INDEX big_table_pk2 RENAME TO big_table_pk;
ALTER INDEX bita_look_fk_i2 RENAME TO bita_look_fk_i;
ALTER INDEX bita_created_date_i2 RENAME TO bita_created_date_i;

4、其他

--在使用DBMS_REDEFINITION期间，假设我们使用COPY_TABLE_DEPENDENTS过程，其索引依然为非分区索引
--须要删除原来的索引之后，然后又一次创建为新的本地分区索引
/*SQL> set timing off
SQL> variable num_errors number

BEGIN
DBMS_REDEFINITION.COPY_TABLE_DEPENDENTS
 (uname=>'LESHAMI',
 orig_table=>'BIG_TABLE',
 int_table=>'BIG_TABLE2',
 num_errors=>:num_errors);
END;
/

SQL> print num_errors

NUM_ERRORS
----------
         0   */
         
--------------------------------------------------------
--例如以下为使用COPY_TABLE_DEPENDENTS依赖对象之后表BIG_TABLE2多出了几个TMP$$开头的索引。可是索引依然为普通索引。而非分区索引  
SQL> @idx_info2 
TABLE_NAME                INDEX_NAME                     CL_NAM               CL_POS STATUS   PAR
------------------------- ------------------------------ -------------------- ------ -------- ---
LOOKUP                    LOOKUP_PK                      ID                        1 VALID    NO
BIG_TABLE                 BIG_TABLE_PK                   ID                        1 VALID    NO
BIG_TABLE                 BITA_CREATED_DATE_I            CREATED_DATE              1 VALID    NO
BIG_TABLE                 BITA_LOOK_FK_I                 LOOKUP_ID                 1 VALID    NO
BIG_TABLE2                TMP$$_BIG_TABLE_PK0            ID                        1 VALID    NO
BIG_TABLE2                TMP$$_BITA_CREATED_DATE_I0     CREATED_DATE              1 VALID    NO
BIG_TABLE2                TMP$$_BITA_LOOK_FK_I0          LOOKUP_ID                 1 VALID    NO

 5 、參考：http://www.oracle-base.com/articles/misc/partitioning-an-existing-table.php