1.模拟环境
创建表插入数据库

[oracle@node1 ~]$ sqlplus chf/xifenfei
SQL*Plus: Release 11.2.0.3.0 Production on Mon Jan 9 16:27:19 2012
Copyright (c) 1982, 2011, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP, Data Mining,
Oracle Database Vault and Real Application Testing options
SQL> create table t_xifenfei(id number,intime date);
Table created.
SQL> DECLARE
  2  i NUMBER;
  3  BEGIN
  4    FOR i IN 1..1000 LOOP
  5      INSERT INTO t_xifenfei VALUES(i,SYSDATE-i);
  6      END LOOP;
  7      COMMIT;
  8  END;
  9  /
PL/SQL procedure successfully completed.
SQL> select count(*) from t_xifenfei;
  COUNT(*)
----------
      1000
SQL> exec dbms_stats.gather_table_stats(USER,'T_XIFENFEI',cascade => TRUE);
PL/SQL procedure successfully completed.

2.无index查询

SQL> set autot trace exp stat
Execution Plan
----------------------------------------------------------
Plan hash value: 548923532
--------------------------------------------------------------------------------
| Id  | Operation         | Name       | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |            |    10 |   120 |     3   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| T_XIFENFEI |    10 |   120 |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter(NVL("INTIME",SYSDATE@!)>=TO_DATE(' 2011-12-31 00:00:00',
              'syyyy-mm-dd hh24:mi:ss'))
Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          7  consistent gets
          0  physical reads
          0  redo size
        770  bytes sent via SQL*Net to client
        519  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          9  rows processed
SQL> set autot off

这里只是做了一个简单的查询，因为这个nvl(intime,sysdate)的条件，无法使用正常的index，所以没有建立intime索引的测试。

3.尝试创建index

SQL>  create index in_t_xifenfei on t_xifenfei (nvl(intime,sysdate)) online nologging;
 create index in_t_xifenfei on t_xifenfei (nvl(intime,sysdate)) online nologging
                                                      *
ERROR at line 1:
ORA-01743: only pure functions can be indexed
SQL> !oerr ora 1743
01743, 00000, "only pure functions can be indexed"
// *Cause: The indexed function uses SYSDATE or the user environment.
// *Action: PL/SQL functions must be pure (RNDS, RNPS, WNDS, WNPS).  SQL
//          expressions must not use SYSDATE, USER, USERENV(), or anything
//          else dependent on the session state.  NLS-dependent functions
//          are OK.
--因为含有sysdate创建函数index失败
SQL> CREATE OR REPLACE FUNCTION f_xifenfei (itime DATE)
  2  RETURN DATE
  3  IS
  4  otime DATE;
  5  BEGIN
  6    otime:=NVL(itime,SYSDATE);
  7    RETURN otime;
  8  END;
  9  /
Function created.
--想采用自定义函数屏蔽掉sysdate在创建index时候的影响
SQL>  create index in_t_xifenfei on t_xifenfei (f_xifenfei(intime)) online nologging;
 create index in_t_xifenfei on t_xifenfei (f_xifenfei(intime)) online nologging
                                           *
ERROR at line 1:
ORA-30553: The function is not deterministic
SQL> !oerr ora 30553
30553, 00000, "The function is not deterministic"
// *Cause:  The function on which the index is defined is not deterministic
// *Action: If the function is deterministic, mark it DETERMINISTIC.  If it
//          is not deterministic (it depends on package state, database state,
//          current time, or anything other than the function inputs) then
//          do not create the index.  The values returned by a deterministic
//          function should not change even when the function is rewritten or
//          recompiled.
--因为函数缺少deterministic不能使用于index上
SQL> CREATE OR REPLACE FUNCTION f_xifenfei (itime DATE)
  2  RETURN DATE deterministic
  3  IS
  4  otime DATE;
  5  BEGIN
  6    otime:=NVL(itime,SYSDATE);
  7    RETURN otime;
  8  END;
  9  /
Function created.
SQL> create index in_t_xifenfei on t_xifenfei (f_xifenfei(intime)) online nologging;
Index created.
--创建函数index成功
SQL> exec dbms_stats.gather_table_stats(USER,'T_XIFENFEI',cascade => TRUE);
PL/SQL procedure successfully completed.

4.再次查询
确定已经使用函数index，达到在index中使用sysdate函数index的目的。

SQL> set autot on  exp stat
SQL> select * from t_xifenfei where f_xifenfei(intime)>=to_date('2011-12-31','yyyy-mm-dd');
Execution Plan
----------------------------------------------------------
Plan hash value: 2005404611
---------------------------------------------------------------------------------------------
| Id  | Operation                   | Name          | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |               |    10 |   200 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T_XIFENFEI    |    10 |   200 |     3   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | IN_T_XIFENFEI |    10 |       |     2   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
   2 - access("CHF"."F_XIFENFEI"("INTIME")>=TO_DATE(' 2011-12-31 00:00:00',
              'syyyy-mm-dd hh24:mi:ss'))
Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          5  consistent gets
          0  physical reads
          0  redo size
        770  bytes sent via SQL*Net to client
        519  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          9  rows processed

5.总结说明
5.1)通过函数屏蔽函数index的时候，不能使用sysdate
5.2)在创建函数时，需要指定deterministic关键字