-----正常执行计划
set autotrace traceonly
set linesize 1000
select /*+index(t idx_object_id)*/ * from t where object_id=19;
Execution Plan
----------------------------------------------------------
Plan hash value: 2041828949
---------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 207 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1
| 207 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN |
IDX_OBJECT_ID | 1 | | 1 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=19)
----在误操作drop 表t 后，立即flashback drop；
但是之前相应的索引已经被rename了，但是oracle依然可以这个这个rename后的索引
SQL> drop table t;
SQL> flashback table t to before drop;
-----异常执行计划
SQL> select * from t where object_id=19;
Execution Plan
----------------------------------------------------------
Plan hash value: 329240726
--------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 207 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 | 207 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN |
BIN$GVgNy7hUF5HgUFAK8RIOcA==$0 | 1 | | 1 (0)| 00:00:01 |------貌似性能没有大影响
--------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=19)
SQL> select index_name,status from user_indexes where table_name=‘T‘;
BIN$GVgNy7hUF5HgUFAK8RIOcA==$0 VALID
------重命名索引
alter index "BIN$GVgNy7hUF5HgUFAK8RIOcA==$0" rename to IDX_OBJECT_ID;
闪回drop恢复表后sql执行计划异常
原文：http://blog.csdn.net/lixora/article/details/46640987
