在11.2中，Oracle对于全外连接的执行计划进行了优化。
这篇介绍新增的两个相关的HINT。
Oracle在推出了新的执行计划的同时，还提供了两个控制这个执行计划的提示NATIVE_FULL_OUTER_JOIN和NO_NATIVE_FULL_OUTER_JOIN。
这两个HINT的使用十分简单，不需要其他的任何参数。下面继续上一篇文章的例子：
SQL> SELECT /*+ NO_NATIVE_FULL_OUTER_JOIN */ T1.ID, T2.ID
2 FROM T1 FULL OUTER JOIN T2
3 ON T1.ID = T2.ID;
ID ID
--------------------
2 2
3 3
4 4
5 5
6 6
7 7
8 8
1
0
10
9
已选择11行。
执行计划
----------------------------------------------------------
Plan hash value: 2841162349
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 18 | 468 | 17 (6)| 00:00:01 |
| 1 | VIEW | | 18 | 468 | 17 (6)| 00:00:01 |
| 2 | UNION-ALL | | | | | |
|* 3 | HASH JOIN OUTER | | 9 | 234 | 9 (12)| 00:00:01 |
| 4 | TABLE ACCESS FULL| T1 | 9 | 117 | 4 (0)| 00:00:01 |
| 5 | TABLE ACCESS FULL| T2 | 9 | 117 | 4 (0)| 00:00:01 |
|* 6 | HASH JOIN ANTI | | 9 | 234 | 9 (12)| 00:00:01 |
| 7 | TABLE ACCESS FULL| T2 | 9 | 117 | 4 (0)| 00:00:01 |
| 8 | TABLE ACCESS FULL| T1 | 9 | 117 | 4 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("T1"."ID"="T2"."ID"(+))
6 - access("T1"."ID"="T2"."ID")
Note
-----
- dynamic sampling used for this statement (level=2)
统计信息
----------------------------------------------------------
13 recursive calls
0 db block gets
61 consistent gets
0 physical reads
0 redo size
733 bytes sent via SQL*Net to client
520 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
11 rows processed
SQL> SELECT /*+ NATIVE_FULL_OUTER_JOIN */ T1.ID, T2.ID
2 FROM T1 FULL OUTER JOIN T2
3 ON T1.ID = T2.ID;
ID ID
--------------------
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9
10
1
0
已选择11行。
执行计划
----------------------------------------------------------
Plan hash value: 53297166
----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 9 | 234 | 9 (12)| 00:00:01 |
| 1 | VIEW | VW_FOJ_0 | 9 | 234 | 9 (12)| 00:00:01 |
|* 2 | HASH JOIN FULL OUTER| | 9 | 234 | 9 (12)| 00:00:01 |
| 3 | TABLE ACCESS FULL | T1 | 9 | 117 | 4 (0)| 00:00:01 |
| 4 | TABLE ACCESS FULL | T2 | 9 | 117 | 4 (0)| 00:00:01 |
----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("T1"."ID"="T2"."ID")
Note
-----
- dynamic sampling used for this statement (level=2)
统计信息
----------------------------------------------------------
7 recursive calls
0 db block gets
31 consistent gets
0 physical reads
0 redo size
733 bytes sent via SQL*Net to client
520 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
11 rows processed
如果两个HINT同时存在，则Oracle选择NO_NATIVE_FULL_OUTER_JOIN提示生效，而忽略NATIVE_FULL_OUTER_JOIN：
SQL> SELECT /*+ NATIVE_FULL_OUTER_JOIN NO_NATIVE_FULL_OUTER_JOIN */ T1.ID, T2.ID
2 FROM T1 FULL OUTER JOIN T2
3 ON T1.ID = T2.ID;
ID ID
--------------------
2 2
3 3
4 4
5 5
6 6
7 7
8 8
1
0
10
9
已选择11行。
执行计划
----------------------------------------------------------
Plan hash value: 2841162349
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 18 | 468 | 17 (6)| 00:00:01 |
| 1 | VIEW | | 18 | 468 | 17 (6)| 00:00:01 |
| 2 | UNION-ALL | | | | | |
|* 3 | HASH JOIN OUTER | | 9 | 234 | 9 (12)| 00:00:01 |
| 4 | TABLE ACCESS FULL| T1 | 9 | 117 | 4 (0)| 00:00:01 |
| 5 | TABLE ACCESS FULL| T2 | 9 | 117 | 4 (0)| 00:00:01 |
|* 6 | HASH JOIN ANTI | | 9 | 234 | 9 (12)| 00:00:01 |
| 7 | TABLE ACCESS FULL| T2 | 9 | 117 | 4 (0)| 00:00:01 |
| 8 | TABLE ACCESS FULL| T1 | 9 | 117 | 4 (0)| 00:00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("T1"."ID"="T2"."ID"(+))
6 - access("T1"."ID"="T2"."ID")
Note
-----
- dynamic sampling used for this statement (level=2)
统计信息
----------------------------------------------------------
13 recursive calls
0 db block gets
61 consistent gets
0 physical reads
0 redo size
733 bytes sent via SQL*Net to client
520 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
11 rows processed
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