rename 表操作后index是否依然可用
今天群里有人问起rename 表操作对index的影响。今天简单说一下：
首先ORACLE官方文档对RENAME操作的说明如下：
Use theRENAME statement to rename a table, view, sequence, or private synonym.
-
Oracle Database automatically transfers integrity constraints, indexes, and grants on the old object to the new object.
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Oracle Database invalidates all objects that depend on the renamed object, such as views, synonyms, and stored procedures and functions that refer to a renamed table.
［可以使用rename语句来rename一个表，视图，序列或私有同义词］。
.Oracle数据库自动把旧的对象上的完整性约束，索引，和权限迁移到新的对象上面。
.Oracle数据库上涉及与命名后的对象有关的例如:视图，同义词和存储过程和函数都会失效。
1.使用scott用户创建一个测试表e1和测试索引e1_eno.
SQL> create table e1 as select * from emp;
Table created.
SQL> create index e1_eno on e1(empno);
Index created.
2.分析执行计划。
SQL> explain plan for select * from e1 where empno>7500;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 12 | 1044 | 2 (0)| 00:0
0:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| E1 | 12 | 1044 | 2 (0)| 00:0
0:01 |
|* 2 | INDEX RANGE SCAN | E1_ENO | 12 | | 1 (0)| 00:0
0:01 |
3.查看index情况。
SQL> select index_name,table_owner,table_name,status from user_indexes where index_name='E1_ENO';
INDEX_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME STATUS
------------------------------ --------
E1_ENO SCOTT
E1 VALID
4.进行rename操作.
SQL> rename e1 to e2;
Table renamed.
5.查询索引情况：
SQL> select index_name,table_owner,table_name,status from user_indexes where index_name='E1_ENO';
INDEX_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME STATUS
------------------------------ --------
E1_ENO SCOTT
E2 VALID
6.按照第二步进行分析，执行计划如下：
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 12 | 1044 | 2 (0)| 00:0
0:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| E2 | 12 | 1044 | 2 (0)| 00:0
0:01 |
|* 2 | INDEX RANGE SCAN | E1_ENO | 12 | | 1 (0)| 00:0
发现更改表名后，索引也同时跟着变动，依旧有效。
7.再次更换为e1看看索引情况：
SQL> rename e2 to e1;
Table renamed.
SQL> select index_name,table_owner,table_name,status from user_indexes where index_name='E1_ENO';
INDEX_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME STATUS
------------------------------ --------
E1_ENO SCOTT
E1 VALID
发现索引再次随着表的更改也进行了同步变动。
8.根据第2步再次查看执行计划：
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 12 | 1044 | 2 (0)| 00:0
0:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| E1 | 12 | 1044 | 2 (0)| 00:0
0:01 |
|* 2 | INDEX RANGE SCAN | E1_ENO | 12 | | 1 (0)| 00:0
0:01 |
--------------------------------------------------------------------------------
总结：由此可知：rename 表后，相应的索引会随着表的变动同步变动。依旧是有效的。不需要我们手动修改。
我们也可以测试一下rename 表后，同义词是否有效：
1.使用scott给e1表创建一个同义词s_e.
create synonym s_e for e1;
2.查询同义词信息
SQL> select synonym_name,table_owner,table_name from user_synonyms;
SYNONYM_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME
------------------------------
S_E SCOTT
E1
3.重命名
SQL> rename e1 to e2;
Table renamed.
4.查询s_e
SQL> select synonym_name,table_owner,table_name from user_synonyms;
SYNONYM_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME
------------------------------
S_E SCOTT
E1
SQL> select * from s_e;
select * from s_e
*
ERROR at line 1:
ORA-00980: synonym translation is no longer valid
5.重新更改为e1.
SQL> rename e2 to e1;
Table renamed.
SQL> select synonym_name,table_owner,table_name from user_synonyms;
SYNONYM_NAME TABLE_OWNER
------------------------------ ------------------------------
TABLE_NAME
------------------------------
S_E SCOTT
E1
6.查询s_e
发现ok.
总结：rename表后，同义词不会同步，因此rename表后，同义词失效。
我们再测试一下rename表对视图的影响：
1.在e1表的基础上创建视图v_e1
SQL> create view v_e1 as select empno,ename,sal from e1;
View created.
SQL> select * from v_e1;
EMPNO ENAME SAL
---------- ---------- ----------
7369 SMITH 800
7499 ALLEN 1600
7521 WARD 1250
2.rename 表
SQL> rename e1 to e2;
Table renamed.
3.验证一下view是否可用。
EMPNO ENAME SAL
---------- ---------- ----------
7369 SMITH 800
7499 ALLEN 1600
7521 WARD 1250
EMPNO ENAME SAL
---------- ---------- ----------
7369 SMITH 800
7499 ALLEN 1600
7521 WARD 1250
SQL> select * from v_e1;
select * from v_e1
*
ERROR at line 1:
ORA-04063: view "SCOTT.V_E1" has errors
4.重新改为e1
SQL> rename e2 to e1;
Table renamed.
SQL> select * from v_e1;
EMPNO ENAME SAL
---------- ---------- ----------
7369 SMITH 800
7499 ALLEN 1600
7521 WARD 1250
5.再次验证视图的有效性
SQL> rename e2 to e1;
Table renamed.
SQL> select * from v_e1;
EMPNO ENAME SAL
---------- ---------- ----------
7369 SMITH 800
7499 ALLEN 1600
7521 WARD 1250
总结：rename后，view同同义词一样失效。