Oracle并行添加主键的方法

环境：Oracle 11.2.0.3

需求：生产一张表由于前期设计不当，没有主键。现需要添加主键，数据量很大，想并行建立。

 

1.直接添加,提示ora-3001:未实施的功能;只能单线程建立主键

SQL> alter table t add constraint pk_t primary key (object_id) using index online parallel 2;



alter table t add constraint pk_t primary key (object_id) using index online parallel 2



ORA-03001: 未实施的功能



SQL> alter table t add constraint pk_t primary key (object_id) using index online;



Table altered



SQL> alter table t drop primary key;



Table altered

 

2.考虑先并行添加惟一性索引，再添加主键

SQL> create unique index pk_t on t(object_id) parallel 2 online;



Index created



SQL> alter table t add constraint pk_t primary key (object_id);



Table altered



SQL> alter index pk_t noparallel;



Index altered

 

3.对比主键和惟一性索引的区别

SQL> desc t

Name           Type          Nullable Default Comments

-------------- ------------- -------- ------- --------

OWNER          VARCHAR2(30)  Y                        

OBJECT_NAME    VARCHAR2(128) Y                        

SUBOBJECT_NAME VARCHAR2(30)  Y                        

OBJECT_ID      NUMBER                                 

DATA_OBJECT_ID NUMBER        Y                        

OBJECT_TYPE    VARCHAR2(19)  Y                        

CREATED        DATE          Y                        

LAST_DDL_TIME  DATE          Y                        

TIMESTAMP      VARCHAR2(19)  Y                        

STATUS         VARCHAR2(7)   Y                        

TEMPORARY      VARCHAR2(1)   Y                        

GENERATED      VARCHAR2(1)   Y                        

SECONDARY      VARCHAR2(1)   Y                        

NAMESPACE      NUMBER        Y                        

EDITION_NAME   VARCHAR2(30)  Y                        



SQL> alter table t drop primary key;



Table altered



SQL> desc t

Name           Type          Nullable Default Comments

-------------- ------------- -------- ------- --------

OWNER          VARCHAR2(30)  Y                        

OBJECT_NAME    VARCHAR2(128) Y                        

SUBOBJECT_NAME VARCHAR2(30)  Y                        

OBJECT_ID      NUMBER        Y                        

DATA_OBJECT_ID NUMBER        Y                        

OBJECT_TYPE    VARCHAR2(19)  Y                        

CREATED        DATE          Y                        

LAST_DDL_TIME  DATE          Y                        

TIMESTAMP      VARCHAR2(19)  Y                        

STATUS         VARCHAR2(7)   Y                        

TEMPORARY      VARCHAR2(1)   Y                        

GENERATED      VARCHAR2(1)   Y                        

SECONDARY      VARCHAR2(1)   Y                        

NAMESPACE      NUMBER        Y                        

EDITION_NAME   VARCHAR2(30)  Y                        

总结：

对于已有大量数据的表无法并行建立主键，可以先并行建立惟一性索引然后再加上主键。

主键不能为空，惟一性索引可以为空。