Oracle分区表的层次查询如何才能用到分区？

最近在调优Oracle分区表的层次查询时，发现用不到分区，做了一个实验，发现还是可以用的到的，只是写法上有些要求。

最近在调优Oracle分区表的层次查询时，，发现用不到分区，做了一个实验，发现还是可以用的到的，只是写法上有些要求。

drop table test;

create table test
(
  id  number primary key,
  parent_id number,
  name varchar2(20),
  code varchar2(4)
)
partition by list(code)
(
  partition p1 values('0301'),
  partition p2 values('0302'),
  partition p3 values('0303'),
  partition p4 values('0304'),
  partition p5 values('0305'),
  partition p6 values('0306'),
  partition p7 values('0307'),
  partition p8 values('0308'),
  partition p_default values (default)
);
insert into test values(1,0,'a1','0301');
insert into test values(2,1,'a2','0301');
insert into test values(3,2,'a3','0301');
insert into test values(4,3,'a4','0301');
insert into test values(5,0,'a5','0302');
insert into test values(6,5,'a6','0302');
insert into test values(7,6,'a7','0302');
insert into test values(8,7,'a8','0302');
insert into test values(9,8,'a9','0302');
insert into test values(10,0,'a10','0303');
insert into test values(11,0,'a11','0304');
insert into test values(12,0,'a12','0306');
insert into test values(13,0,'a13','0307');
insert into test values(14,0,'a14','0308');
insert into test values(15,10,'a15','0303');
insert into test values(16,11,'a16','0304');
insert into test values(17,12,'a17','0306');
insert into test values(18,13,'a18','0307');
insert into test values(19,14,'a19','0308');
commit;

exec dbms_stats.gather_table_stats(user,'test',cascade => true);

SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE    11.2.0.1.0      Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> set autotrace traceonly
SQL> select * from test t
    start with t.id = 12
    connect by prior t.id = t.parent_id;
执行计划
----------------------------------------------------------
Plan hash value: 6144290
----------------------------------------------------------------------------------------------------------------
| Id  | Operation                              | Name | Rows  | Bytes | Cost (%CPU)| Time    | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------
|  0 | SELECT STATEMENT                        |      |    19 |  798 |    16  (7)| 00:00:01 |      |      |
|*  1 |  CONNECT BY NO FILTERING WITH START-WITH|      |      |      |            |          |      |      |
|  2 |  PARTITION LIST ALL                    |      |    19 |  285 |    15  (0)| 00:00:01 |    1 |    9 |
|  3 |    TABLE ACCESS FULL                    | TEST |    19 |  285 |    15  (0)| 00:00:01 |    1 |    9 |
----------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
  1 - access("T"."PARENT_ID"=PRIOR "T"."ID")
      filter("T"."ID"=12)
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        55  consistent gets
          0  physical reads
          0  redo size
        557  bytes sent via SQL*Net to client
        360  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          2  sorts (memory)
          0  sorts (disk)
          2  rows processed

SQL> select * from test t
    start with t.id = 12
            and t.code = '0306'
    connect by prior t.id = t.parent_id;
执行计划
----------------------------------------------------------
Plan hash value: 6144290
----------------------------------------------------------------------------------------------------------------
| Id  | Operation                              | Name | Rows  | Bytes | Cost (%CPU)| Time    | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------
|  0 | SELECT STATEMENT                        |      |    19 |  798 |    16  (7)| 00:00:01 |      |      |
|*  1 |  CONNECT BY NO FILTERING WITH START-WITH|      |      |      |            |          |      |      |
|  2 |  PARTITION LIST ALL                    |      |    19 |  285 |    15  (0)| 00:00:01 |    1 |    9 |
|  3 |    TABLE ACCESS FULL                    | TEST |    19 |  285 |    15  (0)| 00:00:01 |    1 |    9 |
----------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
  1 - access("T"."PARENT_ID"=PRIOR "T"."ID")
      filter("T"."ID"=12 AND "T"."CODE"='0306')
统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
        55  consistent gets
          0  physical reads
          0  redo size
        557  bytes sent via SQL*Net to client
        360  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          2  sorts (memory)
          0  sorts (disk)
          2  rows processed