Oracle 12.2新特性----在线把非分区表转为分区表

在Oracle12.2版本之前，如果想把一个非分区表转为分区表常用的有这几种方法：1、建好分区表然后insert into select 把数据插入到分区表中；2、使用在线重定义(DBMS_REDEFINITION)的方法。它们的币是：第一种方法，如果对表有频繁的DML操作，尤其是update操作，就需要停业务来做转换。第二种方法可以在线进行操作，不需要停业务，但操作步骤比较复杂，且可能出错。

Oracle12cR2版本中提供了一种新特性，一条语句就可以把非分区表转换为分区表，语法如下：

ALTER TABLE table_name MODIFY table_partitioning_clauses
  [ filter_condition ]
  [ ONLINE ]
  [ UPDATE INDEXES [ ( index { local_partitioned_index | global_partitioned_index | GLOBAL }
                     [, index { local_partitioned_index | global_partitioned_index | GLOBAL } ]... )
                   ]
  ]

下面来测试一下这个新特性

1、创建测试表及相关索引，并查看状态

zx@ORA12C>create table emp as select * from scott.emp;

Table created.

zx@ORA12C>create index idx_emp_no on emp(empno);

Index created.

zx@ORA12C>create index idx_emp_job on emp(job);

Index created.

zx@ORA12C>col table_name for a30
zx@ORA12C>col index_name for a30
zx@ORA12C>select table_name,partitioned from user_tables where table_name='EMP';

TABLE_NAME                     PAR
------------------------------ ---
EMP                            NO

zx@ORA12C>select index_name,partitioned,status from user_indexes where table_name='EMP';

INDEX_NAME                     PAR STATUS
------------------------------ --- --------
IDX_EMP_NO                     NO  VALID
IDX_EMP_JOB                    NO  VALID

2、使用alter table语句，执行分区表转换操作

zx@ORA12C>alter table emp modify
  2    partition by range (deptno) interval (10)
  3    ( partition p1 values less than (10),
  4      partition p2 values less than (20)
  5    ) online
  6  ;

Table altered.

3、查看现在的表和索引的状态

zx@ORA12C>select table_name,partitioned from user_tables where table_name='EMP';

TABLE_NAME                     PAR
------------------------------ ---
EMP                            YES

zx@ORA12C>select index_name,partitioned,status from user_indexes where table_name='EMP';

INDEX_NAME                     PAR STATUS
------------------------------ --- --------
IDX_EMP_NO                     NO  VALID
IDX_EMP_JOB                    NO  VALID

zx@ORA12C>select table_name,partition_name from user_tab_partitions where table_name='EMP';

TABLE_NAME                     PARTITION_NAME
------------------------------ ------------------------------
EMP                            P1
EMP                            P2
EMP                            SYS_P405
EMP                            SYS_P406

现在表EMP已经被转换为分区表了，索引转换为分区索引，但索引状态是正常的。

4、如果想在转换表时同时转换索引可以使用UPDATE INDEXES子句

zx@ORA12C>alter table emp modify
  2    partition by range (deptno) interval (10)
  3    ( partition p1 values less than (10),
  4      partition p2 values less than (20)
  5    ) online
  6    update indexes
  7    (idx_emp_no local)
  8  ;

Table altered.

zx@ORA12C>col table_name for a30
zx@ORA12C>col index_name for a30
zx@ORA12C>select table_name,partitioned from user_tables where table_name='EMP';

TABLE_NAME                     PAR
------------------------------ ---
EMP                            YES

zx@ORA12C>select index_name,partitioned,status from user_indexes where table_name='EMP';

INDEX_NAME                     PAR STATUS
------------------------------ --- --------
IDX_EMP_NO                     YES N/A
IDX_EMP_JOB                    NO  VALID

zx@ORA12C>select table_name,partition_name from user_tab_partitions where table_name='EMP';

TABLE_NAME                     PARTITION_NAME
------------------------------ ------------------------------
EMP                            P1
EMP                            P2
EMP                            SYS_P403
EMP                            SYS_P404

zx@ORA12C>select index_name,partition_name,status from user_ind_partitions where index_name='IDX_EMP_NO';

INDEX_NAME                     PARTITION_NAME                 STATUS
------------------------------ ------------------------------ --------
IDX_EMP_NO                     P1                             USABLE
IDX_EMP_NO                     P2                             USABLE
IDX_EMP_NO                     SYS_P403                       USABLE
IDX_EMP_NO                     SYS_P404                       USABLE

从上面的执行结果来看，不仅表EMP转换为分区表，而且索引IDX_EMP_NO也转换分区索引，所有索引状态均正常。

下面是官方文档里的一些注意事项：

When using the UPDATE INDEXES clause, note the following.

• This clause can be used to change the partitioning state of indexes and storage properties of the indexes being converted.

• The specification of the UPDATE INDEXES clause is optional.

  Indexes are maintained both for the online and offline conversion to a partitioned table.

• This clause cannot change the columns on which the original list of indexes are defined.

• This clause cannot change the uniqueness property of the index or any other index property.

• If you do not specify the tablespace for any of the indexes, then the following tablespace defaults apply.

  • Local indexes after the conversion collocate with the table partition.

  • Global indexes after the conversion reside in the same tablespace of the original global index on the non-partitioned table.

• If you do not specify the INDEXES clause or the INDEXES clause does not specify all the indexes on the original non-partitioned table, then the following default behavior applies for all unspecified indexes.

  • Global partitioned indexes remain the same and retain the original partitioning shape.

  • Non-prefixed indexes become global nonpartitioned indexes.

  • Prefixed indexes are converted to local partitioned indexes.

    Prefixed means that the partition key columns are included in the index definition, but the index definition is not limited to including the partitioning keys only.

  • Bitmap indexes become local partitioned indexes, regardless whether they are prefixed or not.

    Bitmap indexes must always be local partitioned indexes.

• The conversion operation cannot be performed if there are domain indexes.

参考：http://docs.oracle.com/database/122/VLDBG/evolve-nopartition-table.htm#VLDBG-GUID-5FDB7D59-DD05-40E4-8AB4-AF82EA0D0FE5