因为需要将一张上亿我们要记录的表修改为分区表，所以尝试使用联机重定义来给表增加新列与分区的方法来实现，下面是一个测试的例子，操作系统是Oracle Linux 7.1,数据库为12.2.0.1,原始表为emp_redef，该表存储在hr方案中:
SQL> desc hr.emp_redef Name Type Nullable Default Comments ------------- ------------ -------- ------- -------- EMPLOYEE_ID NUMBER(6) FIRST_NAME VARCHAR2(20) Y LAST_NAME VARCHAR2(25) JOB_ID VARCHAR2(10) DEPARTMENT_ID NUMBER(4) Y
表emp_redef将按以下规则来进行联机重定义:
.增加新列mgr,hiredate,sal与bonus
.新列bonus被初始化为0
.列department_id的值由10开始增加
.表将被重定义为范围分区表，分区键为employee_id。
联机重定义操作如下:
1.用要执行联机重定义操作的用户登录数据库
SQL> conn pm/pm@jypdb Connected.
2.验证表emp_redef是否可以执行联机重定义。在这种情况下，可以使用主键或伪主键来来进行验证。
SQL> exec dbms_redefinition.can_redef_table(uname=>'HR',tname=>'EMP_REDEF',options_flag=>dbms_redefinition.cons_use_pk); PL/SQL procedure successfully completed.
3.创建一个中间表hr.int_emp_redef
SQL> create table hr.int_emp_redef 2 ( 3 employee_id NUMBER(6) not null, 4 first_name VARCHAR2(20), 5 last_name VARCHAR2(25) not null, 6 job_id VARCHAR2(10) not null, 7 department_id NUMBER(4) not null, 8 mgr NUMBER(5), 9 hiredate DATE DEFAULT(sysdate), 10 sal NUMBER(7,2), 11 bonus NUMBER(7,2) DEFAULT(0) 12 ) 13 partition by range(employee_id) 14 ( 15 partition emp200 values less than(200) tablespace users, 16 partition emp400 values less than(400) tablespace users 17 ); Table created
4.开始重定义操作
SQL> begin 2 dbms_redefinition.start_redef_table( 3 uname => 'hr', 4 orig_table => 'emp_redef', 5 int_table => 'int_emp_redef', 6 col_mapping => 'employee_id employee_id, first_name first_name,last_name last_name, job_id job_id, department_id+10 department_id,0 bonus', 7 options_flag => DBMS_REDEFINITION.CONS_USE_PK); 8 end; 9 / PL/SQL procedure successfully completed.
5.复制依赖对象(自动对表hr.int_emp_redef创建任何触发器，索引，物化视图日志，授权与约束)
SQL> declare 2 num_errors pls_integer; 3 begin 4 dbms_redefinition.copy_table_dependents( 5 uname => 'hr', 6 orig_table => 'emp_redef', 7 int_table => 'int_emp_redef', 8 copy_indexes => DBMS_REDEFINITION.CONS_ORIG_PARAMS, 9 copy_triggers => TRUE, 10 copy_constraints => TRUE, 11 copy_privileges => TRUE, 12 ignore_errors => TRUE, 13 num_errors => num_errors); 14 end; 15 / PL/SQL procedure successfully completed.
注意，在调用这个过程时ignore_errors参数需要设置为TRUE。原因是中间表创建了主键约束，并且当执行copye_table_dependents过程来试图从原始表复制主键约束与索引时会发生错误。可以忽略这些错误，但必须执行下一步操作中的查询来查看是否还存在其它错误。
6.查询dba_redefinition_errors视图来查看错误信息
SQL> set long 8000
SQL> set pages 8000
SQL> column object_name heading 'object name' format a20
SQL> column base_table_name heading 'base table name' format a10
SQL> column ddl_txt heading 'ddl that caused error' format a40
SQL> select object_name, base_table_name, ddl_txt from dba_redefinition_errors;
object name base table ddl that caused error
-------------------- ---------- ----------------------------------------
SYS_C0023200 EMP_REDEF ALTER TABLE "HR"."INT_EMP_REDEF" MODIFY
("LAST_NAME" CONSTRAINT "TMP$$_SYS_C0023
2000" NOT NULL ENABLE NOVALIDATE)
SYS_C0023201 EMP_REDEF ALTER TABLE "HR"."INT_EMP_REDEF" MODIFY
("JOB_ID" CONSTRAINT "TMP$$_SYS_C0023201
0" NOT NULL ENABLE NOVALIDATE)
2 rows selected.
上面的错误信息是说中间表的last_name与job_id列为not null，而原因表为null，这种错误可以忽略。
7.同步中间表hr.int_emp_redef
SQL> begin 2 dbms_redefinition.sync_interim_table( 3 uname => 'hr', 4 orig_table => 'emp_redef', 5 int_table => 'int_emp_redef'); 6 end; 7 / PL/SQL procedure successfully completed.
8.完成重定义操作
SQL> begin 2 dbms_redefinition.finish_redef_table( 3 uname => 'hr', 4 orig_table => 'emp_redef', 5 int_table => 'int_emp_redef'); 6 end; 7 / PL/SQL procedure successfully completed.
表hr.emp_redef只会以排他模式被锁定很短的时间来结束重定义操作。在操作完成后，表hr.emp_redef将使用hr.int_emp_redef表的所有属性来重定义。
SQL> desc hr.emp_redef Name Type Nullable Default Comments ------------- ------------ -------- --------- -------- EMPLOYEE_ID NUMBER(6) FIRST_NAME VARCHAR2(20) Y LAST_NAME VARCHAR2(25) JOB_ID VARCHAR2(10) DEPARTMENT_ID NUMBER(4) MGR NUMBER(5) Y HIREDATE DATE Y (sysdate) SAL NUMBER(7,2) Y BONUS NUMBER(7,2) Y (0)
SQL> select dbms_metadata.get_ddl(object_type =>'TABLE',name =>'EMP_REDEF',schema => 'HR') from dual;
DBMS_METADATA.GET_DDL(OBJECT_TYPE=>'TABLE',NAME=>'EMP_REDEF',SCHEMA=>'HR')
--------------------------------------------------------------------------------
CREATE TABLE "HR"."EMP_REDEF"
( "EMPLOYEE_ID" NUMBER(6,0) NOT NULL ENABLE,
"FIRST_NAME" VARCHAR2(20),
"LAST_NAME" VARCHAR2(25) NOT NULL ENABLE,
"JOB_ID" VARCHAR2(10) NOT NULL ENABLE,
"DEPARTMENT_ID" NUMBER(4,0) NOT NULL ENABLE,
"MGR" NUMBER(5,0),
"HIREDATE" DATE DEFAULT (sysdate),
"SAL" NUMBER(7,2),
"BONUS" NUMBER(7,2) DEFAULT (0),
CONSTRAINT "EMP_REDEF_EMP_ID_PK" PRIMARY KEY ("EMPLOYEE_ID")
USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS" ENABLE
) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
STORAGE(
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS"
PARTITION BY RANGE ("EMPLOYEE_ID")
(PARTITION "EMP200" VALUES LESS THAN (200) SEGMENT CREATION IMMEDIATE
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
STORAGE(INITIAL 8388608 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS" ,
PARTITION "EMP400" VALUES LESS THAN (400) SEGMENT CREATION IMMEDIATE
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
STORAGE(INITIAL 8388608 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "USERS" )
1 row selected.
可以看到表hr.emp_redef已经成功能联机重定义
9.等任何查询中间表的语句执行完成后将其删除，而且中间表在重定义后其结构就变成了原始表的表结构
SQL> desc hr.int_emp_redef Name Type Nullable Default Comments ------------- ------------ -------- ------- -------- EMPLOYEE_ID NUMBER(6) Y FIRST_NAME VARCHAR2(20) Y LAST_NAME VARCHAR2(25) JOB_ID VARCHAR2(10) DEPARTMENT_ID NUMBER(4) Y SQL> drop table hr.int_emp_redef purge; Table dropped
到此，联机重定义表hr.emp_redef就操作完成。