实验: Oracle中表shrink与move后index的状态

1 move时实验

SQL> create table my_objects_move tablespace ASSM as select * from all_objects where rownum < 20000;

Table created

SQL> create index i_my_objects_move on my_objects_move (object_id);

Index created

SQL> delete from my_objects_move where object_name like '%C%';

7546 rows deleted

SQL> delete from my_objects_move where object_name like '%U%';

2959 rows deleted

SQL> commit;

Commit complete

SQL> alter table my_objects_move move;

Table altered

SQL> select index_name, status

2 from user_indexes

3 where index_name = 'I_MY_OBJECTS_MOVE';

INDEX_NAME STATUS

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

I_MY_OBJECTS_MOVE UNUSABLE

SQL> alter index I_MY_OBJECTS_MOVE rebuild;

Index altered

SQL> select index_name, status

2 from user_indexes

3 where index_name = 'I_MY_OBJECTS_MOVE';

INDEX_NAME STATUS

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

I_MY_OBJECTS_MOVE VALID

2 shrink时实验

SQL> create table my_objects tablespace ASSM as select * from all_objects where rownum < 20000;

Table created

SQL> create index i_my_objects on my_objects (object_id);

Index created

SQL> delete from my_objects where object_name like '%C%';

7546 rows deleted

SQL> delete from my_objects where object_name like '%U%';

2959 rows deleted

SQL> commit;

Commit complete

SQL> alter table my_objects enable row movement;

Table altered

SQL> alter table my_objects shrink space;

Table altered

SQL> select index_name, status

2 from user_indexes

3 where index_name = 'I_MY_OBJECTS';

INDEX_NAME STATUS

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

I_MY_OBJECTS VALID

3 结论

shrink在移动行数据时，也一起维护了index上相应行的数据rowid的信息，当然shrink过程中用来维护index的成本也会比较高。而表move后index的状态是UNUSABLE的,需要进行rebuild。