Oracle之分区表和索引优化，分区表字段回表

-- 范围分区示例
drop table part_table purge;
--注意，此分区为范围分区

--例子1
create table part_table (id number,deal_date date,area_code number,nbr number,contents varchar2(4000))
           partition by range (deal_date)
           (
           partition p_201701 values less than (TO_DATE('2017-02-01', 'YYYY-MM-DD')),
           partition p_201702 values less than (TO_DATE('2017-03-01', 'YYYY-MM-DD')),
           partition p_201703 values less than (TO_DATE('2017-04-01', 'YYYY-MM-DD')),
           partition p_201704 values less than (TO_DATE('2017-05-01', 'YYYY-MM-DD')),
           partition p_201705 values less than (TO_DATE('2017-06-01', 'YYYY-MM-DD')),
           partition p_201706 values less than (TO_DATE('2017-07-01', 'YYYY-MM-DD')),
           partition p_201707 values less than (TO_DATE('2017-08-01', 'YYYY-MM-DD')),
           partition p_201708 values less than (TO_DATE('2017-09-01', 'YYYY-MM-DD')),
           partition p_201709 values less than (TO_DATE('2017-10-01', 'YYYY-MM-DD')),
           partition p_201710 values less than (TO_DATE('2017-11-01', 'YYYY-MM-DD')),
           partition p_201711 values less than (TO_DATE('2017-12-01', 'YYYY-MM-DD')),
           partition p_201712 values less than (TO_DATE('2018-01-01', 'YYYY-MM-DD')),
           partition p_201801 values less than (TO_DATE('2018-02-01', 'YYYY-MM-DD')),
           partition p_201802 values less than (TO_DATE('2018-03-01', 'YYYY-MM-DD')),
           partition p_max values less than (maxvalue)
           )
           ;




alter table part_table modify nbr not null;
--以下是插入2017年一整年日期随机数和表示山东地区号含义（591到599）的随机数记录，共有10万条，如下：
insert into part_table (id,deal_date,area_code,nbr,contents)
      select rownum,
             to_date( to_char(sysdate-365,'J')+TRUNC(DBMS_RANDOM.VALUE(0,365)),'J'),
             ceil(dbms_random.value(591,599)),
             ceil(dbms_random.value(18900000001,18999999999)),
             rpad('*',400,'*')
        from dual
      connect by rownum <= 100000;
commit;


--以下是插入2018年一整年日期随机数和表示山东地区号含义（591到599）的随机数记录，共有10万条，如下：
insert into part_table (id,deal_date,area_code,nbr,contents)
      select rownum,
             to_date( to_char(sysdate,'J')+TRUNC(DBMS_RANDOM.VALUE(0,365)),'J'),
             ceil(dbms_random.value(591,599)),
             ceil(dbms_random.value(18900000001,18999999999)),
             rpad('*',400,'*')
        from dual
      connect by rownum <= 100000;
commit;

create index idx_part_id on part_table (id) ;
create index idx_part_nbr on part_table (nbr) local;

--统计信息系统一般会自动收集，这只是首次建成表后需要操作一下，以方便测试
exec dbms_stats.gather_table_stats(ownname => 'LJB',tabname => 'part_table',estimate_percent => 10,method_opt=> 'for all indexed columns',cascade=>TRUE) ;  


set autotrace on 
set linesize 1000


select max(nbr) max_nbr from part_table partition(p_201705);
执行计划
------------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name         | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |              |     1 |     8 |     2   (0)| 00:00:01 |       |       |
|   1 |  SORT AGGREGATE             |              |     1 |     8 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE    |              |     1 |     8 |     2   (0)| 00:00:01 |     5 |     5 |
|   3 |    INDEX FULL SCAN (MIN/MAX)| IDX_PART_NBR |     1 |     8 |     2   (0)| 00:00:01 |     5 |     5 |
------------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          2  consistent gets




select max(nbr) max_nbr
  from part_table
 where deal_date >= TO_DATE('2017-05-01', 'YYYY-MM-DD')
   and deal_date < TO_DATE('2017-06-01', 'YYYY-MM-DD');
执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |                |     1 |    17 |   170   (0)| 00:00:03 |       |       |
|   1 |  SORT AGGREGATE         |                |     1 |    17 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|                |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
|   3 |    TABLE ACCESS FULL    | part_table |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
----------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        568  consistent gets




select count(*) max_nbr from part_table partition(p_201705);
执行计划
------------------------------------------------------------------------------------------------
| Id  | Operation               | Name         | Rows  | Cost (%CPU)| Time     | Pstart| Pstop |
------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |              |     1 |     8   (0)| 00:00:01 |       |       |
|   1 |  SORT AGGREGATE         |              |     1 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|              |  8716 |     8   (0)| 00:00:01 |     5 |     5 |
|   3 |    INDEX FAST FULL SCAN | IDX_PART_NBR |  8716 |     8   (0)| 00:00:01 |     5 |     5 |
------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
         29  consistent gets   

select count(*) max_nbr
  from part_table
 where deal_date >= TO_DATE('2017-05-01', 'YYYY-MM-DD')
   and deal_date < TO_DATE('2017-06-01', 'YYYY-MM-DD');
执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |                |     1 |     9 |   170   (0)| 00:00:03 |       |       |
|   1 |  SORT AGGREGATE         |                |     1 |     9 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|                |    22 |   198 |   170   (0)| 00:00:03 |     5 |     5 |
|   3 |    TABLE ACCESS FULL    | part_table |    22 |   198 |   170   (0)| 00:00:03 |     5 |     5 |
----------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        568  consistent gets
        
        
           
select sum(nbr) max_nbr from part_table partition(p_201705);
执行计划
--------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name         | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
--------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |              |     1 |     8 |     8   (0)| 00:00:01 |       |       |
|   1 |  SORT AGGREGATE         |              |     1 |     8 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|              |  8716 | 69728 |     8   (0)| 00:00:01 |     5 |     5 |
|   3 |    INDEX FAST FULL SCAN | IDX_PART_NBR |  8716 | 69728 |     8   (0)| 00:00:01 |     5 |     5 |
--------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
         29  consistent gets
            
select sum(nbr) max_nbr
  from part_table
 where deal_date >= TO_DATE('2017-05-01', 'YYYY-MM-DD')
   and deal_date < TO_DATE('2017-06-01', 'YYYY-MM-DD');
执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |                |     1 |    17 |   170   (0)| 00:00:03 |       |       |
|   1 |  SORT AGGREGATE         |                |     1 |    17 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|                |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
|   3 |    TABLE ACCESS FULL    | part_table |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
----------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        568  consistent gets   
  
select distinct(nbr) from part_table partition(p_201705);
执行计划
--------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name         | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
--------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |              |  8660 | 69280 |     9  (12)| 00:00:01 |       |       |
|   1 |  HASH UNIQUE            |              |  8660 | 69280 |     9  (12)| 00:00:01 |       |       |
|   2 |   PARTITION RANGE SINGLE|              |  8716 | 69728 |     8   (0)| 00:00:01 |     5 |     5 |
|   3 |    INDEX FAST FULL SCAN | IDX_PART_NBR |  8716 | 69728 |     8   (0)| 00:00:01 |     5 |     5 |
--------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
         29  consistent gets
          0  physical reads
          0  redo size
     152890  bytes sent via SQL*Net to client
       6741  bytes received via SQL*Net from client
        577  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
       8635  rows processed
              
select distinct(nbr)
  from part_table
 where deal_date >= TO_DATE('2017-05-01', 'YYYY-MM-DD')
   and deal_date < TO_DATE('2017-06-01', 'YYYY-MM-DD');
执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |                |    22 |   374 |   171   (1)| 00:00:03 |       |       |
|   1 |  HASH UNIQUE            |                |    22 |   374 |   171   (1)| 00:00:03 |       |       |
|   2 |   PARTITION RANGE SINGLE|                |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
|   3 |    TABLE ACCESS FULL    | part_table |    22 |   374 |   170   (0)| 00:00:03 |     5 |     5 |
----------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        568  consistent gets
          0  physical reads
          0  redo size
     152886  bytes sent via SQL*Net to client
       6741  bytes received via SQL*Net from client
        577  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
       8635  rows processed   
   


select count(*)
  from part_table
 where deal_date >= TO_DATE('2017-05-01 00:00:00', 'YYYY-MM-DD hh24:mi:ss')
   and deal_date <= TO_DATE('2017-06-01 00:00:00', 'YYYY-MM-DD hh24:mi:ss');
  COUNT(*)
----------
    8635
执行计划
------------------------------------------------------------------------------------------------------------
| Id  | Operation                 | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT          |                |     1 |     9 |   340   (1)| 00:00:05 |       |       |
|   1 |  SORT AGGREGATE           |                |     1 |     9 |            |          |       |       |
|   2 |   PARTITION RANGE ITERATOR|                |   497 |  4473 |   340   (1)| 00:00:05 |     5 |     6 |
|*  3 |    TABLE ACCESS FULL      | part_table |   497 |  4473 |   340   (1)| 00:00:05 |     5 |     6 |
------------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
       1136  consistent gets 
                
select count(*)
  from part_table
 where deal_date >= TO_DATE('2017-05-01 00:00:00', 'YYYY-MM-DD hh24:mi:ss')
   and deal_date < TO_DATE('2017-06-01 00:00:00', 'YYYY-MM-DD hh24:mi:ss');      
  COUNT(*)
----------
    8635   
执行计划
----------------------------------------------------------------------------------------------------------
| Id  | Operation               | Name           | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |                |     1 |     9 |   170   (0)| 00:00:03 |       |       |
|   1 |  SORT AGGREGATE         |                |     1 |     9 |            |          |       |       |
|   2 |   PARTITION RANGE SINGLE|                |    22 |   198 |   170   (0)| 00:00:03 |     5 |     5 |
|   3 |    TABLE ACCESS FULL    | part_table |    22 |   198 |   170   (0)| 00:00:03 |     5 |     5 |
----------------------------------------------------------------------------------------------------------
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        568  consistent gets   


结论：当查询时候，用到分区表字段但是索引没有分区表字段，oracle需要回表，造成性能损耗