分类目录归档：Oracle

Oracle 11g增加列,并带默认值的新特性

发表于 2012 年 7 月 14 日由惜分飞

在11g以前,如果要在一个大表中增加一列,并设置默认值,那将是一个非常悲剧的事情.有些时候不得不选择在线重定义功能来实现该需求.而在11g中增加新列并设置默认值,只是简单的修改数据字典来实现该功能,大大提供效率
10g加列(默认值)

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE    10.2.0.1.0      Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

SQL> create table t_xifenfei 
  2  as select object_id,object_name from dba_objects;

Table created.

SQL> select count(*) from t_xifenfei;

  COUNT(*)
----------
     49827

SQL> desc t_xifenfei
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OBJECT_ID                                          NUMBER
 OBJECT_NAME                                        VARCHAR2(128)

SQL> set timing on                                                                      
SQL> alter table t_xifenfei add c_xff varchar2(100) default 'www.xifenfei.com' not null;

Table altered.

Elapsed: 00:00:06.13
--使用了6秒钟

SQL> select   rowid,
  2   dbms_rowid.rowid_relative_fno(rowid)rel_fno,
  3   dbms_rowid.rowid_block_number(rowid)blockno,
  4   dbms_rowid.rowid_row_number(rowid) rowno
  5  from t_xifenfei where object_name='OBJ$';

ROWID                 REL_FNO    BLOCKNO      ROWNO
------------------ ---------- ---------- ----------
AAAMwJAAEAAAAB8AAr          4        124         43

SQL> alter system dump datafile 4 block 124;

System altered.

Elapsed: 00:00:00.08

11g增加列(默认值)

SQL> select * from v$version;

BANNER
-----------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production

SQL> create table t_xifenfei 
  2  as select object_id,object_name from dba_objects;

Table created.

SQL> select count(*) from t_xifenfei;

  COUNT(*)
----------
     74605

SQL> select   rowid,
  2   dbms_rowid.rowid_relative_fno(rowid)rel_fno,
  3   dbms_rowid.rowid_block_number(rowid)blockno,
  4   dbms_rowid.rowid_row_number(rowid) rowno
  5  from t_xifenfei where object_name='OBJ$';

ROWID                 REL_FNO    BLOCKNO      ROWNO
------------------ ---------- ---------- ----------
AAASpRAAEAAAACrAAu          4        171         46

SQL> alter system dump datafile 4 block 171;

System altered.


SQL> set timing on
SQL> alter table t_xifenfei add c_xff varchar2(100) default 'www.xifenfei.com' not null;

Table altered.

Elapsed: 00:00:00.19
--只是使用了0.19秒

SQL> select   rowid,
  2   dbms_rowid.rowid_relative_fno(rowid)rel_fno,
  3   dbms_rowid.rowid_block_number(rowid)blockno,
  4   dbms_rowid.rowid_row_number(rowid) rowno
  5  from t_xifenfei where object_name='OBJ$';

ROWID                 REL_FNO    BLOCKNO      ROWNO
------------------ ---------- ---------- ----------
AAASpRAAEAAAACrAAu          4        171         46

Elapsed: 00:00:00.04
SQL> alter system dump datafile 4 block 171;

System altered.

通过10g和11g的增加相同列和默认值的对比可以发现,11g的速度要比10g快很多很多,下面我们通过上面dump出来相关的数据块来分析原因
dump分析
11g增加列之前dump

tab 0, row 0, @0x1f74
tl: 12 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 15
col  1: [ 5]  49 43 4f 4c 24
tab 0, row 1, @0x1f66
tl: 14 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 2f
col  1: [ 7]  49 5f 55 53 45 52 31
tab 0, row 2, @0x1f5b
tl: 11 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 1d
col  1: [ 4]  43 4f 4e 24

11g增加列之后dump

tab 0, row 0, @0x1f74
tl: 12 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 15
col  1: [ 5]  49 43 4f 4c 24
tab 0, row 1, @0x1f66
tl: 14 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 2f
col  1: [ 7]  49 5f 55 53 45 52 31
tab 0, row 2, @0x1f5b
tl: 11 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 1d
col  1: [ 4]  43 4f 4e 24
tab 0, row 3, @0x1f4f
tl: 12 fb: --H-FL-- lb: 0x0  cc: 2
col  0: [ 2]  c1 10
col  1: [ 5]  55 4e 44 4f 24

10g增加列之后dump
因为10g在没有增加列之前的dump和11g未增加列之前类似,所以未dump出来

tab 0, row 0, @0x1f63
tl: 29 fb: --H-FL-- lb: 0x2  cc: 3
col  0: [ 2]  c1 15
col  1: [ 5]  49 43 4f 4c 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 1, @0x1f44
tl: 31 fb: --H-FL-- lb: 0x2  cc: 3
col  0: [ 2]  c1 2d
col  1: [ 7]  49 5f 55 53 45 52 31
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 2, @0x1f28
tl: 28 fb: --H-FL-- lb: 0x2  cc: 3
col  0: [ 2]  c1 1d
col  1: [ 4]  43 4f 4e 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 3, @0x1f0b
tl: 29 fb: --H-FL-- lb: 0x2  cc: 3
col  0: [ 2]  c1 10
col  1: [ 5]  55 4e 44 4f 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d

对比发现11g在增加列之后,以前的数据dump出来的内容未有任何改变.也就是说:在10g中,我们增加一个列和默认值,会自动的增加到真实的数据中,而在11g中增加列和默认值并未真的加到11g的表中已经存在的数据中.
11g中插入新数据dump测试

SQL>  insert into chf.t_xifenfei(object_id,object_name)
  2  select object_id,object_name FROM DBA_OBJECTS;

74605 rows created.

SQL> commit;

Commit complete.

SQL> ALTER SYSTEM FLUSH BUFFER_CACHE;

System altered.

SQL> /

System altered.
--建议刷新

SQL> 
SQL> 
SQL> select   rowid,
  2   dbms_rowid.rowid_relative_fno(rowid)rel_fno,
  3   dbms_rowid.rowid_block_number(rowid)blockno,
  4   dbms_rowid.rowid_row_number(rowid) rowno
  5  from chf.t_xifenfei where object_name='OBJ$';

ROWID                 REL_FNO    BLOCKNO      ROWNO
------------------ ---------- ---------- ----------
AAASpRAAEAAAACrAAu          4        171         46
AAASpRAAEAAAB5TAAu          4       7763         46

SQL> ALTER SYSTEM DUMP DATAFILE 4 BLOCK 7763;

System altered.

--dump内容
tab 0, row 0, @0x4e3
tl: 29 fb: --H-FL-- lb: 0x1  cc: 3
col  0: [ 2]  c1 15
col  1: [ 5]  49 43 4f 4c 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 1, @0x500
tl: 31 fb: --H-FL-- lb: 0x1  cc: 3
col  0: [ 2]  c1 2f
col  1: [ 7]  49 5f 55 53 45 52 31
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 2, @0x51f
tl: 28 fb: --H-FL-- lb: 0x1  cc: 3
col  0: [ 2]  c1 1d
col  1: [ 4]  43 4f 4e 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d
tab 0, row 3, @0x53b
tl: 29 fb: --H-FL-- lb: 0x1  cc: 3
col  0: [ 2]  c1 10
col  1: [ 5]  55 4e 44 4f 24
col  2: [16]  77 77 77 2e 78 69 66 65 6e 66 65 69 2e 63 6f 6d

通过这里看看出:在11g中后续插入的数据,默认值也插入到数据文件中

发表在 Oracle | 一条评论

今天kaums给客户做培训11g新特性,发现还真的有不少挺好的新东西,但是以前没有怎么去关注的他们,在后续的几篇中,陆续整理处理.
DDL_LOCK_TIMEOUT specifies a time limit for how long DDL statements will wait in a DML lock queue. The default value of zero indicates a status of NOWAIT. The maximum value of 1,000,000 seconds will result in the DDL statement waiting forever to acquire a DML lock.
If a lock is not acquired before the timeout period expires, then an error is returned.
数据库ddl_lock_timeout参数

SQL> select * from v$version;

BANNER
---------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for Linux: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production

SQL> show parameter ddl_lock_timeout;

NAME                                 TYPE       VALUE
------------------------------------ ---------- --------------
ddl_lock_timeout                     integer    0

ddl_lock_timeout默认值测试(同以前版本)

--会话1
SQL> set time on
10:27:57 SQL> create table t_xifenfei as
10:28:05   2  select * from dba_users;

Table created.

Elapsed: 00:00:00.08
10:28:17 SQL> delete from t_xifenfei where username='CHF';

1 row deleted.

--会话2
SQL> set timing on
SQL> ALTER TABLE T_XIFENFEI DROP COLUMN AUTHENTICATION_TYPE;
ALTER TABLE T_XIFENFEI DROP COLUMN AUTHENTICATION_TYPE
            *
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired


Elapsed: 00:00:00.01

设置ddl_lock_timeout超时测试

--会话1
10:28:17 SQL> delete from t_xifenfei where username='CHF';

1 row deleted.

--会话2
SQL>  ALTER SESSION SET ddl_lock_timeout=10;

Session altered.

Elapsed: 00:00:00.00
SQL> ALTER TABLE T_XIFENFEI DROP COLUMN AUTHENTICATION_TYPE;
ALTER TABLE T_XIFENFEI DROP COLUMN AUTHENTICATION_TYPE
            *
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired


Elapsed: 00:00:10.01

设置ddl_lock_timeout未超时测试

--会话2
SQL> ALTER SESSION SET ddl_lock_timeout=30;

Session altered.

Elapsed: 00:00:00.00

--会话1
10:30:00 SQL> COMMIT;

Commit complete.

Elapsed: 00:00:00.00

--会话2
SQL> ALTER TABLE T_XIFENFEI DROP COLUMN AUTHENTICATION_TYPE;

Table altered.

Elapsed: 00:00:07.91

在以前的版本中ddl操作是nowait等待,通过实验可以发现ddl_lock_timeout可以在一定程度上解决因为我们不清楚这个表是否有dml操作而导致ddl操作不能进行的情况,从一定程度上减少了自己去尝试ddl操作,或者查询相关视图然后找出相关会话,然后kill掉对应数据的情况,可以说是在修改表结构的时候一个很不错的新特性.

发表在 Oracle | 一条评论

使用flashback query恢复被删除plsql

发表于 2012 年 7 月 9 日由惜分飞

今天一个朋友在11g中误删除生产中的一个过程,让他通过对dba_source视图的flashback query找回该过程.
从10g及其以后的版本中,如果被删除的plsql被及时发现(undo 未被覆盖掉)可以使用flashback query功能实现恢复.
创建plsql并删除

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE    10.2.0.1.0      Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

SQL> create or replace PROCEDURE  p_test_del(in_put varchar2) as
  2  begin
  3  dbms_output.put_line(in_put);
  4  end;
  5  /

Procedure created.

SQL> set serveroutput on
SQL> exec p_test_del('www.xifenfei.com');
www.xifenfei.com

PL/SQL procedure successfully completed.

SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;

TO_CHAR(SYSDATE,'YY
-------------------
2012-07-02 08:34:45

SQL> drop  PROCEDURE  p_test_del;

Procedure dropped.

恢复plsql

SQL> set pagesize 0
SQL> column text format a4000
SQL> spool /tmp/get_delete_proc.xff
SQL> SELECT text
  2         FROM DBA_source AS OF TIMESTAMP TO_TIMESTAMP('2012-07-02 08:34:45', 'YYYY-MM-DD HH24:MI:SS')
  3        WHERE OWNER = 'CHF' AND NAME = 'P_TEST_DEL' ORDER BY LINE;
PROCEDURE  p_test_del(in_put varchar2) as
begin
dbms_output.put_line(in_put);
end;

SQL> spool off;
SQL> !more /tmp/get_delete_proc.xff
SQL> SELECT text
  2         FROM DBA_source AS OF TIMESTAMP TO_TIMESTAMP('2012-07-02 08:34:45', 'YYYY-MM-DD HH24:MI:SS')
  3        WHERE OWNER = 'CHF' AND NAME = 'P_TEST_DEL' ORDER BY LINE;
create PROCEDURE  p_test_del(in_put varchar2) as 
begin                         
dbms_output.put_line(in_put); 
end;        

SQL> spool off;

重建plsql

SQL> create PROCEDURE  p_test_del(in_put varchar2) as 
  2  begin                                     
  3  dbms_output.put_line(in_put);             
  4  end; 
  5  /

Procedure created.

SQL> set serveroutput on
SQL> exec p_test_del('惜分飞');
惜分飞

PL/SQL procedure successfully completed.

发表在 Oracle备份恢复 | 3 条评论

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分类目录归档：Oracle

Oracle 11g增加列,并带默认值的新特性

Oracle 11G的DDL_LOCK_TIMEOUT参数

使用flashback query恢复被删除plsql

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分类目录归档：Oracle

Oracle 11g增加列,并带默认值的新特性

Oracle 11G的DDL_LOCK_TIMEOUT参数

使用flashback query恢复被删除plsql

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