online 方式创建索引触发trigger怎么办？

背景：

1. 为防止误删除数据，我们会在数据库中创建trigger，禁止对表进行drop或者truncate。
2. 通常给表创建索引时候，为了避免创建索引过程中锁表引起性能问题，我们会要求创建索引时候加上online参数。

 
普通创建索引 和 online 方式创建索引的区别：

① 普通创建索引的命令create index会先锁表，然后再创建索引，如果表中数据量很大，会造成阻塞DML语句；

② create index online 允许其它会话修改索引字段，但如果修改索引字段的会话没有commit或是rollbak，则索引创建会被阻塞。

但是加online字段有一些限制：

 
实验：

1. 创建trigger

  
  
  

   
   
   -- 创建trigger，禁止对表进行drop和truncate操作SQL> conn / as sysdbaConnected.SQL> create or replace trigger trigger_undroptable BEFORE DROP or TRUNCATE ON DATABASE begin end if; if ora_login_user not in ('SYS','SYSTEM') THEN if upper(dictionary_obj_type) ='TABLE' THEN Raise_application_error (-20001,'Please not do DROP or TRUNCATE Table,You will be Caught!!!'); end if; end if; end; /Trigger created.
  
  
  

2. 创建测试表

  
  
  

   
   
   SQL> conn sxc/sxcConnected.SQL> create table t(a int primary key,b int,c int,d int);Table created.SQL> set line222SQL> select index_name,table_name from user_indexes;INDEX_NAME TABLE_NAME----------------------------------- ----------------------------------------SYS_C0014935 T-- 插入数据SQL> BEGIN FOR X IN 1 .. 1000 LOOP INSERT INTO t VALUES (x,x+1,x+2,x+3); COMMIT; DBMS_LOCK.SLEEP(0.2); END LOOP;END;/
  
  
  

3. 使用online方式创建索引

  
  
  

   
   
   -- 使用online 方式创建索引SQL> create index idx1 on t (b) online;create index idx1 on t (b) online *ERROR at line 1:ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4SQL> select index_name,table_name,STATUS from user_indexes;INDEX_NAME TABLE_NAME STATUS------------------------------------------- ------------------------------------------------------------SYS_C0014935 T VALIDIDX1 T VALIDSYS_IOT_TOP_94130 SYS_JOURNAL_94129 VALID 
  
  
  

 结论：可以看到创建索引时，触发了trigger_undroptable触发器，创建报错。但是我们发现IDX1索引也创建好了，并且多出了SYS_JOURNAL_94129表和索引，状态都是VALID。 

4. 校验索引

  
  
  

   
   
   SQL> set line222SQL> set autotrace off SQL> alter session set statistics_level=all ;Session altered.SQL> VARIABLE id NUMBERSQL> EXECUTE :id := 10;PL/SQL procedure successfully completed.SQL> SELECT count(*) FROM t WHERE b < :id; COUNT(*)---------- 8SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));PLAN_TABLE_OUTPUT------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------SQL_ID d3f4gyz6wsjmn, child number 0-------------------------------------SELECT count(*) FROM t WHERE b < :idPlan hash value: 3080277828------------------------------------------------------------------------------------| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers |------------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 1 | | 1 |00:00:00.01 | 2 || 1 | SORT AGGREGATE | | 1 | 1 | 1 |00:00:00.01 | 2 |PLAN_TABLE_OUTPUT------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|* 2 | INDEX RANGE SCAN| IDX1 | 1 | 8 | 8 |00:00:00.01 | 2 |------------------------------------------------------------------------------------Predicate Information (identified by operation id):--------------------------------------------------- 2 - access("B"<:ID)Note----- - dynamic sampling used for this statement (level=2)23 rows selected.
  
  
  

 结论：可以看到SQL语句执行计划中，用到了索引IDX1 ，说明可以正常使用。 

5. 删除索引

  
  
  

   
   
   SQL> drop index idx1;drop index idx1 *ERROR at line 1:ORA-08104: this index object 94129 is being online built or rebuilt-- 删除index 报错，无法正常删除。-- 解决办法：-- 查询object_id 94129 就是我们创建的indexSQL> set line222SQL> col owner for a10SQL> col OBJECT_NAME for a10SQL> select owner,object_name,object_id,object_type from dba_objects where object_id='94129';OWNER OBJECT_NAM OBJECT_ID OBJECT_TYPE---------- ---------- ---------- --------------------------------------SXC IDX1 94129 INDEX[[email protected] trace]$ sqlplus / as sysdbaSQL*Plus: Release 11.2.0.4.0 Production on Wed Aug 3 15:32:19 2022Copyright (c) 1982, 2013, Oracle. All rights reserved.Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing optionsSQL> declare 2 done boolean; 3 begin 4 done:=dbms_repair.online_index_clean(94129); ---OBJECT_ID 5 end; 6 /PL/SQL procedure successfully completed.-- 再次查询 idx1 没有了SQL> select index_name,table_name from user_indexes;INDEX_NAME TABLE_NAME------------------------------------------------------------ -----------------------------------------------SYS_C0014935 T
  
  
  

6. 通过10046 trace 查看创建索引过程

  
  
  

   
   
   SQL> set autotrace offSQL> alter session set statistics_level=typical; Session altered.SQL> alter session set events '10046 trace name context forever,level 12';Session altered.SQL> create index idx1 on t (b) online;create index idx1 on t (b) online *ERROR at line 1:ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4SQL> alter session set events '10046 trace name context off'; Session altered.SQL> select SPID from v$process where addr=(select PADDR from v$session where sid=(select distinct sid from v$mystat));SPID------------------------------------------------1820-- 查看trace文件[[email protected] trace]$ tkprof LHR11G_ora_1820.trc LHR11G_ora_1820.txt 
  
  
  

结论：可以发现使用online参数建立索引要建立一个临时SYS_JOURNAL_94130 IOT表，索引创建完成后再drop table时，触发到trigger。

7. rebuild index online

  
  
  

   
   
   -- 普通方式rebuild 正常SQL> alter index SYS_C0014935 rebuild;Index altered.-- oline方式rebuild 报错SQL> alter index SYS_C0014935 rebuild online;alter index SYS_C0014935 rebuild online*ERROR at line 1:ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4ORA-00604: error occurred at recursive SQL level 2ORA-20001: Please not do DROP or TRUNCATE Table,You will be Caught!!!ORA-06512: at line 4
  
  
  

结论：使用online 方式rebuild index 同样也会触发trigger报错。

 
综上： 当我们数据库中存在禁止drop table trigger 时候，我们使用online 方式创建索引，需要先disable trigger 或者使用trigger 约束范围以外的用户进行创建。