oracle分区的exchange操作非常快，那原理是什么呢？下面我们来做个实验：
SQL> create table test (id number(3));
表已创建。
SQL> insert into test values (1);
已创建 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));
表已创建。
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 P1 180150 180150
TEST_PART P2 180151 180151
TEST_PART 180149
SQL> select * from test;
ID
----------
1
SQL> select * from test_part;
未选定行
SQL> alter table test_part exchange partition p1 with table test;
表已更改。
SQL> select * from test;
未选定行
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 P1 180150 180148
TEST_PART P2 180151 180151
TEST_PART 180149
exchange只是在oracle的数据字典中修改了分区和表的结构。数据并未发生任何修改，因此速度很快。更详细一点就是只是把不同object_id 对应的data_object_id交换了一下，而segment本身并没有改变，和物理存储位置无关，但必须是分区表和非分区表 之间才可以交换。