ORA-01502 state unusable错误成因和解决方法(二)-数据库专栏,ORACLE

sql> create table t(a number);

table created.

现在，我们建立一个唯一索引来看看：
sql> create unique index idx_t on t(a);

index created.

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=t;         

no rows selected

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       valid

sql> insert into t values(1);

1 row created.

sql> commit;

commit complete.

将索引手工修改为unusable状态（模拟发生索引失效的情况）：
sql> alter index idx_t unusable;

index altered.

sql>  select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       unusable

我们看到这是，已经不能正常往表中插入数据：
sql> insert into t values(2);
insert into t values(2)
*
error at line 1:
ora-01502: index misc.idx_t or partition of such index is in unusable state

首先，我们通过重建索引（rebuild index）的方法来解决问题：
sql> alter index idx_t rebuild;

index altered.

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       valid

sql> insert into t values(2);

1 row created.

sql> commit;

commit complete.

sql>

现在我们再次模拟索引失效(unusable状态)：
sql> alter index idx_t unusable;

index altered.

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       unusable

sql> insert into t values(3);
insert into t values(3)
*
error at line 1:
ora-01502: index misc.idx_t or partition of such index is in unusable state

然后，看看是否可以通过设置参数skip_unusable_indexes=true来解决问题：
sql> alter session set skip_unusable_indexes=true;

session altered.

sql> insert into t values(3);
insert into t values(3)
*
error at line 1:
ora-01502: index misc.idx_t or partition of such index is in unusable state

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       unusable

sql> alter index idx_t rebuild;

index altered.

sql> select index_name,index_type,tablespace_name,table_type,status from user_indexes where index_name=idx_t;

index_name                     index_type                  tablespace_name                table_type  status
—————————— ————————— —————————— ———– ——–
idx_t                          normal                      data_dynamic                   table       valid

sql> insert into t values(3);

1 row created.

sql> commit;

commit complete.

sql>
很显然，对于unique index，通过简单的设置参数是不能解决问题的，要解决unique index 失效的问题，只能通过重建索引来实现。