3.在部分分区上创建本地索引和全局索引。

Oracle 12c 新特性 --- 分区表的局部索引

全局的部分索引：只对那些需要索引的分区创建索引，别的分区不会创建。 
本地索引：如果对表分区打开索引，则索引分区可用，否则不可用。 您可以通过在索引或索引分区级别指定USABLE / UNUSABLE来覆盖此行为。  
这个功能不支持唯一索引，full是默认的模式。

 

 

CREATE TABLE orders (
  order_id NUMBER(12),
  order_date DATE CONSTRAINT order_date_nn NOT NULL,
  order_mode VARCHAR2(8),
  customer_id NUMBER(6) CONSTRAINT order_customer_id_nn NOT NULL,
  order_status NUMBER(2),
  order_total NUMBER(8,2),
  sales_rep_id NUMBER(6),
  promotion_id NUMBER(6),
  CONSTRAINT order_mode_lov CHECK (order_mode in ('direct','online')),
  CONSTRAINT order_total_min CHECK (order_total >= 0))
   INDEXING OFF
   PARTITION BY RANGE (ORDER_DATE)
   (PARTITION ord_p1 VALUES LESS THAN (TO_DATE('01-MAR-1999','DD-MON-YYYY')) 
     INDEXING ON,
   PARTITION ord_p2 VALUES LESS THAN (TO_DATE('01-JUL-1999','DD-MON-YYYY')) 
     INDEXING OFF,
   PARTITION ord_p3 VALUES LESS THAN (TO_DATE('01-OCT-1999','DD-MON-YYYY')) 
     INDEXING ON,
   PARTITION ord_p4 VALUES LESS THAN (TO_DATE('01-MAR-2000','DD-MON-YYYY')),
   PARTITION ord_p5 VALUES LESS THAN (TO_DATE('01-MAR-2010','DD-MON-YYYY')));

创建全局索引
CREATE INDEX ORDERS_ORDER_TOTAL_GIDX ON ORDERS (ORDER_TOTAL)
   GLOBAL INDEXING PARTIAL;
SQL>  select index_name,index_type,partitioned,orphaned_entries,indexing from user_indexes;

INDEX_NAME                     INDEX_TYPE                  PAR ORP INDEXIN
------------------------------ --------------------------- --- --- -------
PK_DEPT                        NORMAL                      NO  NO  FULL
PK_EMP                         NORMAL                      NO  NO  FULL
ORDERS_ORDER_TOTAL_GIDX        NORMAL                      NO  NO  PARTIAL              <----------PARTIAL  
SQL>  select * from user_ind_partitions ;

no rows selected
下面创建本地分区索引
create index idx_orders_local on orders(order_date) local;
select index_name,partition_name,status from user_ind_partitions ;
SQL>  select index_name,partition_name,status from user_ind_partitions ;

INDEX_NAME           PARTITION_NAME       STATUS
-------------------- -------------------- --------
IDX_ORDERS_LOCAL     ORD_P1               USABLE
IDX_ORDERS_LOCAL     ORD_P2               USABLE
IDX_ORDERS_LOCAL     ORD_P3               USABLE
IDX_ORDERS_LOCAL     ORD_P4               USABLE
IDX_ORDERS_LOCAL     ORD_P5               USABLE

SELECT table_name,
           partition_name,
           indexing
    FROM   user_tab_partitions
    ORDER BY 1,2; 
TABLE_NAME           PARTITION_NAME       INDE
-------------------- -------------------- ----
ORDERS               ORD_P1               ON
ORDERS               ORD_P2               ON
ORDERS               ORD_P3               ON
ORDERS               ORD_P4               ON
ORDERS               ORD_P5               ON

SCOTT@orcl01>ALTER TABLE ORDERS  MODIFY PARTITION ORD_P5 INDEXING OFF;

SELECT table_name,
           partition_name,
           indexing
    FROM   user_tab_partitions
    ORDER BY 1,2; 
TABLE_NAME           PARTITION_NAME       INDE
-------------------- -------------------- ----
ORDERS               ORD_P1               ON
ORDERS               ORD_P2               ON
ORDERS               ORD_P3               ON
ORDERS               ORD_P4               ON
ORDERS               ORD_P5               OFF

SQL> drop index IDX_ORDERS_LOCAL ;
 
 添加索引部分子句可以将索引创建为部分索引。非索引的分区被标记为不可用。

SQL> create index IDX_ORDERS_LOCAL on orders(order_date) local indexing partial;          <----------PARTIAL  

Index created.

SQL>  select index_name,partition_name,status from user_ind_partitions ;

INDEX_NAME           PARTITION_NAME       STATUS
-------------------- -------------------- --------
IDX_ORDERS_LOCAL     ORD_P1               USABLE
IDX_ORDERS_LOCAL     ORD_P2               USABLE
IDX_ORDERS_LOCAL     ORD_P3               USABLE
IDX_ORDERS_LOCAL     ORD_P4               USABLE
IDX_ORDERS_LOCAL     ORD_P5               UNUSABLE
 


SCOTT@orcl01>ALTER TABLE ORDERS  MODIFY PARTITION ORD_P5 INDEXING ON;
COTT@orcl01>ALTER TABLE ORDERS  MODIFY PARTITION ORD_P4 INDEXING OFF; 
 
SELECT table_name,
           partition_name,
           indexing
    FROM   user_tab_partitions
    ORDER BY 1,2;
    

TABLE_NAME           PARTITION_NAME       INDE
-------------------- -------------------- ----
ORDERS               ORD_P1               ON
ORDERS               ORD_P2               ON
ORDERS               ORD_P3               ON
ORDERS               ORD_P4               OFF
ORDERS               ORD_P5               ON            <------------------
 
 
 SCOTT@orcl01>select index_name,partition_name,status from user_ind_partitions ;

INDEX_NAME                                                  PARTITION_NAME       STATUS
----------------------------------------------------------- -------------------- ----------
IDX_ORDERS_LOCAL                                            ORD_P1               USABLE
IDX_ORDERS_LOCAL                                            ORD_P2               USABLE
IDX_ORDERS_LOCAL                                            ORD_P3               USABLE
IDX_ORDERS_LOCAL                                            ORD_P4               UNUSABLE
IDX_ORDERS_LOCAL                                            ORD_P5               USABLE         <------------------

 

 

 

 

效果：不可用的分区索引为全表扫描。 可用的分区索引 走索引

SCOTT@orcl01>SELECT * FROM     ORDERS PARTITION(ORD_P4) where order_total=5 ;               <-----PARTITION(ORD_P4)

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 3905487950

-------------------------------------------------------------------------------------------------
| Id  | Operation              | Name   | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
-------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT       |        |     1 |    93 |     3   (0)| 00:00:01 |       |       |
|   1 |  PARTITION RANGE SINGLE|        |     1 |    93 |     3   (0)| 00:00:01 |     4 |     4 |
|*  2 |   TABLE ACCESS FULL    | ORDERS |     1 |    93 |     3   (0)| 00:00:01 |     4 |     4 |   <-----全表
-------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - filter("ORDER_TOTAL"=5)

Note
-----
   - dynamic statistics used: dynamic sampling (level=2)


Statistics
----------------------------------------------------------
         23  recursive calls
          0  db block gets
         10  consistent gets
          0  physical reads
          0  redo size
        920  bytes sent via SQL*Net to client
        414  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          0  rows processed

SCOTT@orcl01>SELECT * FROM     ORDERS PARTITION(ORD_P1) where order_total=5 ;                  <-----PARTITION(ORD_P1)

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 1855914208

--------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                  | Name                    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
--------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                           |                         |     1 |    93 |     1   (0)| 00:00:01 |       |       |
|   1 |  TABLE ACCESS BY GLOBAL INDEX ROWID BATCHED| ORDERS                  |     1 |    93 |     1   (0)| 00:00:01 |     1 |     1 |
|*  2 |   INDEX RANGE SCAN                         | ORDERS_ORDER_TOTAL_GIDX |     1 |       |     1   (0)| 00:00:01 |       |       |
--------------------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("ORDER_TOTAL"=5)
       filter(TBL$OR$IDX$PART$NUM("ORDERS",0,1,0,ROWID)=1)

Note
-----
   - dynamic statistics used: dynamic sampling (level=2)


Statistics
----------------------------------------------------------
         44  recursive calls
          8  db block gets
         41  consistent gets
          0  physical reads
       1096  redo size
        920  bytes sent via SQL*Net to client
        414  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          0  rows processed

 

 

 

参考文档 

 

http://docs.oracle.com/database/121/NEWFT/chapter12101.htm#NEWFT205

http://docs.oracle.com/database/121/VLDBG/GUID-569F94D0-E6E5-45BB-9626-5506DE18FF00.htm#VLDBG00403

https://oracle-base.com/articles/12c/partial-indexes-for-partitioned-tables-12cr1

http://docs.oracle.com/database/121/CNCPT/schemaob.htm#CNCPT89298