oracle分區的exchange操作非常快，那原理是什么呢？下面我們來做個實驗：

SQL> create table test (id number(3));

表已創建。

SQL> insert into test values (1);

已創建 1 行。

SQL> commit;

提交完成。

SQL> select object_id,data_object_id from user_objects s where s.object_name='TEST';

OBJECT_ID DATA_OBJECT_ID

---------- --------------

180148???????? 180148

SQL> create table test_part(id number(3)) partition by range(id)

2????? (partition p1 values less than (10),

3?????? partition p2 values less than (20));

表已創建。

SQL> col object_name format a20

SQL> col subobject_name format a20

SQL> select object_name,s.subobject_name,object_id, data_object_id

2??? from user_objects s

3?? where s.object_name = 'TEST_PART';

OBJECT_NAME????????? SUBOBJECT_NAME??????? OBJECT_ID DATA_OBJECT_ID

-------------------- -------------------- ---------- --------------

TEST_PART??????????? P1180150???????? 180150TEST_PART??????????? P2?????????????????????? 180151???????? 180151

TEST_PART???????????????????????????????????? 180149

SQL> select * from test;

ID

----------

1

SQL> select * from test_part;

未選定行

SQL> alter table test_part exchange partition p1 with table test;

表已更改。

SQL> select * from test;

未選定行

SQL> select * from test_part;

ID

----------

1

SQL> select * from test_part partition (p1);

ID

----------

1

SQL> select object_id,data_object_id from user_objects s where s.object_name='TEST';

OBJECT_ID DATA_OBJECT_ID

---------- --------------

180148???????? 180150

SQL> select object_name,s.subobject_name,object_id, data_object_id

2??? from user_objects s

3?? where s.object_name = 'TEST_PART';

OBJECT_NAME????????? SUBOBJECT_NAME??? OBJECT_ID?? DATA_OBJECT_ID

-------------------- ---------------- ----------?? --------------

TEST_PART??????????? P1180150???????? 180148TEST_PART??????????? P2???????????????? 180151???????? 180151

TEST_PART?????????????????????????????? 180149

exchange只是在oracle的數據字典中修改了分區和表的結構。數據并未發生任何修改，因此速度很快。更詳細一點就是只是把不同object_id 對應的data_object_id交換了一下，而segment本身并沒有改變，和物理存儲位置無關，但必須是分區表和非分區表 之間才可以交換。

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