今天有人在QQ上问，如何将global的索引改成分区索引？由于在同一个列上不能建不同名的索引，不然会报错：
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除了删除重建索引外，我们其实可以用在线重定义的方法来重构索引，下面是一个例子：
1. 原表和其索引的建立：
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2. 插入数据：
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3. 创建目标表，且索引是local的分区索引：
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4. 进行在线重定义，注意我们在这里是用rowid在进行重定义的，因此options_flag=2，不然会报错ora-12089
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5. 最后完成在线重定义（之前可以多次同步目标表）
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至此，tab2表上的global索引已经改成local索引，后续的措施就是rename索引名至正常的索引名和去掉hidden列，在这里就不继续展开了。
补充：
索引是一般索引还是分区索引，可以看dba_indexes的partitioned字段。如果partitioned字段是YES，说明是分区索引，那么，这个索引是global还是local，可以看dba_part_indexes的LOCALITY字段。
另外，我们还可以看ALIGNMENT字段，看这个索引是基于前导列（prefixed）还是非前导列。(注：global肯定是基于前导列，因为不能建基于非前导列的global索引。而local索引可以基于前导列和非前导列)
SQL> drop table invoices;
Table dropped.
--创建分区表，是range分区：
SQL> CREATE TABLE invoices
2 (invoice_no NUMBER NOT NULL,
3 invoice_date DATE NOT NULL,
4 invoice_area varchar2(200),
5 invoice_serial number,
6 comments VARCHAR2(500),
7 invoice_name varchar2(20)
8 )
9 PARTITION BY RANGE (invoice_date)
10 (PARTITION invoices_q1 VALUES LESS THAN (TO_DATE('01/04/2001', 'DD/MM/YYYY')) TABLESPACE users,
11 PARTITION invoices_q2 VALUES LESS THAN (TO_DATE('01/07/2001', 'DD/MM/YYYY')) TABLESPACE users,
12 PARTITION invoices_q3 VALUES LESS THAN (TO_DATE('01/09/2001', 'DD/MM/YYYY')) TABLESPACE users,
13 PARTITION invoices_q4 VALUES LESS THAN (TO_DATE('01/01/2002', 'DD/MM/YYYY')) TABLESPACE users);
Table created.
--创建global分区索引，分区类型可以和表一样，也可以不一样。这个索引是和表分区类型一样，但是value less值不一样。
SQL> CREATE INDEX idx_glob_inv_ser ON invoices (invoice_serial,comments) GLOBAL
2 PARTITION BY range (invoice_serial)
3 (PARTITION invoices_q1 VALUES LESS THAN (10) TABLESPACE users,
4 PARTITION invoices_q2 VALUES LESS THAN (20) TABLESPACE users,
5 PARTITION invoices_q3 VALUES LESS THAN (30) TABLESPACE users,
6 PARTITION invoices_q4 VALUES LESS THAN (40) TABLESPACE users,
7 PARTITION invoices_qmax VALUES LESS THAN (MAXVALUE) TABLESPACE users);
Index created.
--注意global分区索引，必须使用前导列，及如果索引列是 (comments,invoice_serial)，
--但partition by xx(invoice_serial)用了非前导列，是会报错，不能创建成功的。
SQL> CREATE INDEX idx_glob_inv_date ON invoices (comments,invoice_serial) GLOBAL
2 PARTITION BY hash (invoice_serial) partitions 16;
PARTITION BY hash (invoice_serial) partitions 16
*
ERROR at line 2:
ORA-14038: GLOBAL partitioned index must be prefixed
--创建另一个global分区索引，这个索引的分区类型是和表分区类型不一样的。用了hash分区。但是prefix前导列的原理也是一样的，需要使用前导列。
SQL> CREATE INDEX idx_glob_inv_date ON invoices (comments,invoice_serial) GLOBAL
2 PARTITION BY hash (comments) partitions 16;
Index created.
--创建local索引，注意不能指定partition by的类型的，local索引的分区类型和分区数量必须和table一致，但是可以指定不同的表空间。这个local使用了前导列。
SQL> CREATE INDEX idx_glo_inv_dt ON invoices (invoice_date,invoice_serial) LOCAL
2 (PARTITION invoices_q1 TABLESPACE users,
3 PARTITION invoices_q2 TABLESPACE users,
4 PARTITION invoices_q3 TABLESPACE users,
5 PARTITION invoices_q4 TABLESPACE users);
Index created.
--如果分区数量必须和table不一致，会报错：
SQL> CREATE INDEX idx_glo_inv_dt ON invoices (invoice_date,invoice_serial) LOCAL
2 (PARTITION invoices_q1 TABLESPACE users,
3 PARTITION invoices_q2 TABLESPACE users,
4 PARTITION invoices_q3 TABLESPACE users,
5 PARTITION invoices_q4 TABLESPACE users,
6 PARTITION invoices_q5 TABLESPACE users);
CREATE INDEX idx_glo_inv_dt ON invoices (invoice_date,invoice_serial) LOCAL
*
ERROR at line 1:
ORA-14024: number of partitions of LOCAL index must equal that of the underlying table
--创建local索引，注，local索引可以使用非前导列。而global索引只能使用前导列，不能使用非前导列。
SQL> CREATE INDEX idx_glo_inv_serl ON invoices (invoice_serial,invoice_date) LOCAL
2 (PARTITION invoices_q1 TABLESPACE users,
3 PARTITION invoices_q2 TABLESPACE users,
4 PARTITION invoices_q3 TABLESPACE users,
5 PARTITION invoices_q4 TABLESPACE users);
Index created.
--如果分区数量必须和table不一致，会报错：
SQL> CREATE INDEX idx_glo_inv_serl ON invoices (invoice_serial,invoice_date) LOCAL
2 (PARTITION invoices_q1 TABLESPACE users,
3 PARTITION invoices_q2 TABLESPACE users,
4 PARTITION invoices_q3 TABLESPACE users,
5 PARTITION invoices_q4 TABLESPACE users
6 PARTITION invoices_q5 TABLESPACE users,
7 PARTITION invoices_q6 TABLESPACE users);
PARTITION invoices_q5 TABLESPACE users,
*
ERROR at line 6:
ORA-14010: this physical attribute may not be specified for an index partition
--创建一般索引（即非分区索引）：
SQL> create index idx_glo_inv_comm on invoices (comments);
Index created.
SQL> select index_name,PARTITIONED from dba_indexes where table_name='INVOICES';
INDEX_NAME PARTIT
-------------------- ------
IDX_GLOB_INV_SER YES
IDX_GLOB_INV_DATE YES
IDX_GLO_INV_DT YES
IDX_GLO_INV_SERL YES
IDX_GLO_INV_COMM NO
SQL> select INDEX_NAME,PARTITIONING_TYPE,LOCALITY,ALIGNMENT from dba_part_indexes where table_name='INVOICES';
INDEX_NAME PARTITIONING_TYPE LOCALITY ALIGNMENT
-------------------- ------------------ ------------ ------------------------
IDX_GLOB_INV_SER RANGE GLOBAL PREFIXED
IDX_GLOB_INV_DATE HASH GLOBAL PREFIXED
IDX_GLO_INV_DT RANGE LOCAL PREFIXED
IDX_GLO_INV_SERL RANGE LOCAL NON_PREFIXED参考 https://oracleblog.org/study-note/partition-index-summary/
