ORACLE中修改表的Schema的总结

前阵子遇到一个案例，需要将数据库中的几个表从USER A 移动到USER B下面，在ORACLE中，这个叫做更改表的所有者或者修改表的Schema。其实遇到这种案例，有好几种解决方法。下面我们通过实验来测试、验证一下。首先准备简单测试数据,如下所示:

SQL> CREATE TABLE TEST.KKK

( ID   INT   ,  

  NAME VARCHAR2(12) ,

  CONSTRAINT PK_KKK PRIMARY KEY(ID)

);

Table created.

SQL> INSERT INTO TEST.KKK

  2  VALUES(1000, 'kerry');

1 row created.

SQL> commit;

Commit complete.

方法1： 常规方法，在目标用户下创建表，并拷贝数据过去。

SQL> CREATE TABLE TEST1.KKK( ID  INT, NAME VARCHAR2(12) ,CONSTRAINT PK_KKK PRIMARY KEY (ID));

Table created.

SQL> INSERT INTO TEST1.KKK

  2  SELECT * FROM TEST.KKK;

1 row created.

SQL> COMMIT;

Commit complete.

SQL> DROP TABLE TEST.KKK;

Table dropped.

SQL> 

当然也可以使用CREATE TABLE TEST1.KKK AS SELECT * FROM TEST.KKK; 但是使用这种方式需要注意，索引和约束都无法Copy过去。所以一定要慎用CREATE TABLE AS （CTAS）这种语法。

方法2： 使用expdp/impdp，导出表然后导入表修改表的Schema。使用exp/imp方式也是差不多，在此不做介绍。

[oracle@DB-Server dpdump]$ expdp system/xxxx tables=test.kkk directory=data_pump_dir dumpfile=kkk.dmp logfile=kkk.log;

Export: Release 11.2.0.1.0 - Production on Mon Jul 10 15:57:22 2017

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

Starting "SYSTEM"."SYS_EXPORT_TABLE_01":  system/******** tables=test.kkk directory=data_pump_dir dumpfile=kkk.dmp logfile=kkk.log

Estimate in progress using BLOCKS method...

Processing object type TABLE_EXPORT/TABLE/TABLE_DATA

Total estimation using BLOCKS method: 64 KB

Processing object type TABLE_EXPORT/TABLE/TABLE

Processing object type TABLE_EXPORT/TABLE/INDEX/INDEX

Processing object type TABLE_EXPORT/TABLE/CONSTRAINT/CONSTRAINT

. . exported "TEST"."KKK"                                5.421 KB       1 rows

Master table "SYSTEM"."SYS_EXPORT_TABLE_01" successfully loaded/unloaded

******************************************************************************

Dump file set for SYSTEM.SYS_EXPORT_TABLE_01 is:

/u01/app/oracle/admin/gsp/dpdump/kkk.dmp

Job "SYSTEM"."SYS_EXPORT_TABLE_01" successfully completed at 15:57:26

[oracle@DB-Server dpdump]$ impdp system/xxxx tables=test.kkk directory=data_pump_dir remap_schema=test:test1 dumpfile=kkk.dmp logfile=import.log

Import: Release 11.2.0.1.0 - Production on Mon Jul 10 15:58:07 2017

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

Master table "SYSTEM"."SYS_IMPORT_TABLE_01" successfully loaded/unloaded

Starting "SYSTEM"."SYS_IMPORT_TABLE_01":  system/******** tables=test.kkk directory=data_pump_dir remap_schema=test:test1 dumpfile=kkk.dmp logfile=import.log

Processing object type TABLE_EXPORT/TABLE/TABLE

Processing object type TABLE_EXPORT/TABLE/TABLE_DATA

. . imported "TEST1"."KKK"                               5.421 KB       1 rows

Processing object type TABLE_EXPORT/TABLE/INDEX/INDEX

Processing object type TABLE_EXPORT/TABLE/CONSTRAINT/CONSTRAINT

Job "SYSTEM"."SYS_IMPORT_TABLE_01" successfully completed at 15:58:09

注意上面方法无法移动表到其它表空间，所以，如果你也必须移动表到对应的表空间，那么就必须使用参数remap_tablespace， 如下所示：

impdp system/xxxxx tables=test.kkk directory=data_pump_dir remap_schema=test:test1 remap_tablespace=tbs_test_data:tbs_test1_data dumpfile=kkk.dmp logfile=import.log

方法3：修改系统表obj$、sys.con$等 （这个仅仅作为实验测试而已，不可应用于生产环境）,ASK TOM里面强烈不建议使用这种方法，原文如下，不过不妨碍我们在测试环境玩一玩，了解一下。

SQL> select obj#, owner#, name, namespace from obj$ where name='KKK';

      OBJ#     OWNER# NAME                            NAMESPACE

---------- ---------- ------------------------------ ----------

     93220         85 KKK                                     1

SQL> select user_id , username from dba_users where username in ('TEST', 'TEST1');

   USER_ID USERNAME

---------- ------------------------------

        86 TEST1

        85 TEST

SQL>  update obj$ set owner#=86 where obj#=93220;

1 row updated.

SQL> commit;

Commit complete.

SQL> 

如下所示，更新了系统表obj$后，你会发现TEST.KKK与TEST1.KKK两个表都存在，这个时候可以执行ALTER SYSTEM FLUSH SHARED_POOL命令后，TEST.KKK就不存在了。

SQL> select * from v$mystat where rownum=1;

       SID STATISTIC#      VALUE

---------- ---------- ----------

        12          0          0

SQL> SELECT * FROM TEST.KKK;

        ID NAME

---------- ------------

      1000 kerry

SQL> SELECT * FROM TEST1.KKK;

        ID NAME

---------- ------------

      1000 kerry

SQL> ALTER SYSTEM FLUSH SHARED_POOL;

System altered.

SQL>  SELECT * FROM TEST.KKK;

 SELECT * FROM TEST.KKK

                    *

ERROR at line 1:

ORA-00942: table or view does not exist

SQL>  SELECT * FROM TEST1.KKK;

        ID NAME

---------- ------------

      1000 kerry

SQL> 

另外，更新了系统表obj$后，你会发现索引、约束信息还没有变化，如下所示，OWNER依然为TEST，索引也可以在obj$中更新对应记录，但是约束就必须继续查找

SQL>  SELECT OWNER ,INDEX_NAME , TABLE_NAME FROM DBA_INDEXES WHERE TABLE_NAME='KKK';

OWNER                          INDEX_NAME                     TABLE_NAME

------------------------------ ------------------------------ ------------------------------

TEST                           PK_KKK                         KKK

SQL> COL OWNER FOR A20;

SQL> SELECT OWNER, CONSTRAINT_NAME FROM DBA_CONSTRAINTS WHERE TABLE_NAME='KKK';

OWNER                CONSTRAINT_NAME

-------------------- ------------------------------

TEST                 PK_KKK

SQL> select obj#, owner#, name, namespace from obj$ where name='PK_KKK';

      OBJ#     OWNER# NAME                            NAMESPACE

---------- ---------- ------------------------------ ----------

     93221         85 PK_KKK                                  4

SQL> update obj$ set owner#=86 where obj#=93221;

1 row updated.

SQL> commit;

Commit complete.

SQL> SELECT OWNER ,INDEX_NAME , TABLE_NAME FROM DBA_INDEXES WHERE TABLE_NAME='KKK';

OWNER                INDEX_NAME                     TABLE_NAME

-------------------- ------------------------------ ------------------------------

TEST1                PK_KKK                         KKK

SQL> SELECT OWNER, CONSTRAINT_NAME FROM DBA_CONSTRAINTS WHERE TABLE_NAME='KKK';

OWNER                CONSTRAINT_NAME

-------------------- ------------------------------

TEST                 PK_KKK

SQL> 

而DBA_CONSTRAINTS的定义位于 cdcore.sql中（$ORACLE_HOME/rdbms/admin)中，具体定义如下所示所示（本文测试环境为Oracle 11g），从其定义可以知道，我们必须更新sys.con$中的记录。

create or replace view DBA_CONSTRAINTS

    (OWNER, CONSTRAINT_NAME, CONSTRAINT_TYPE,

     TABLE_NAME, SEARCH_CONDITION, R_OWNER,

     R_CONSTRAINT_NAME, DELETE_RULE, STATUS,

     DEFERRABLE, DEFERRED, VALIDATED, GENERATED,

     BAD, RELY, LAST_CHANGE, INDEX_OWNER, INDEX_NAME,

     INVALID, VIEW_RELATED)

as

select ou.name, oc.name,

       decode(c.type#, 1, 'C', 2, 'P', 3, 'U',

              4, 'R', 5, 'V', 6, 'O', 7,'C', 8, 'H', 9, 'F',

              10, 'F', 11, 'F', 13, 'F', '?'),

       o.name, c.condition, ru.name, rc.name,

       decode(c.type#, 4,

              decode(c.refact, 1, 'CASCADE', 2, 'SET NULL', 'NO ACTION'),

              NULL),

       decode(c.type#, 5, 'ENABLED',

              decode(c.enabled, NULL, 'DISABLED', 'ENABLED')),

       decode(bitand(c.defer, 1), 1, 'DEFERRABLE', 'NOT DEFERRABLE'),

       decode(bitand(c.defer, 2), 2, 'DEFERRED', 'IMMEDIATE'),

       decode(bitand(c.defer, 4), 4, 'VALIDATED', 'NOT VALIDATED'),

       decode(bitand(c.defer, 8), 8, 'GENERATED NAME', 'USER NAME'),

       decode(bitand(c.defer,16),16, 'BAD', null),

       decode(bitand(c.defer,32),32, 'RELY', null),

       c.mtime,

       decode(c.type#, 2, ui.name, 3, ui.name, null),

       decode(c.type#, 2, oi.name, 3, oi.name, null),

       decode(bitand(c.defer, 256), 256,

              decode(c.type#, 4,

                     case when (bitand(c.defer, 128) = 128

                                or o.status in (3, 5)

                                or ro.status in (3, 5)) then 'INVALID'

                          else null end,

                     case when (bitand(c.defer, 128) = 128

                                or o.status in (3, 5)) then 'INVALID'

                          else null end

                    ),

              null),

       decode(bitand(c.defer, 256), 256, 'DEPEND ON VIEW', null)

from sys.con$ oc, sys.con$ rc, sys."_BASE_USER" ou, sys."_BASE_USER" ru,

     sys."_CURRENT_EDITION_OBJ" ro, sys."_CURRENT_EDITION_OBJ" o, sys.cdef$ c,

     sys.obj$ oi, sys.user$ ui

where oc.owner# = ou.user#

  and oc.con# = c.con#

  and c.obj# = o.obj#

  and c.type# != 8        /* don't include hash expressions */

  and (c.type# < 14 or c.type# > 17)    /* don't include supplog cons   */

  and (c.type# != 12)                   /* don't include log group cons */

  and c.rcon# = rc.con#(+)

  and c.enabled = oi.obj#(+)

  and oi.owner# = ui.user#(+)

  and rc.owner# = ru.user#(+)

  and c.robj# = ro.obj#(+)

/

那么我们必须更新sys.con$中记录，如下所示：

SQL> select owner#,name, con# from sys.con$ where name='PK_KKK';

    OWNER# NAME                                 CON#

---------- ------------------------------ ----------

        85 PK_KKK                              19023

SQL> update sys.con$ set owner#=86 where name='PK_KKK';

1 row updated.

SQL> commit;

Commit complete.

SQL> COL OWNER FOR A32;

SQL> SELECT OWNER, CONSTRAINT_NAME FROM DBA_CONSTRAINTS WHERE TABLE_NAME='KKK';

OWNER                            CONSTRAINT_NAME

-------------------------------- ------------------------------

TEST1                            PK_KKK

SQL>

OK，到此基本的几种方法我们已经介绍了,实际场景当中，那些需要修改Schema的表可能会非常大，生产环境完全不能使用方法3这种捷径。如果使用CTAS这种方法，即使使用NOLOGGING和开启并行，也是非常消耗资源和时间的。使用expdp/impdp 稍微好一些，但是也不能避免一些资源开销。 还有一种方法就是使用exchange partition，exchange只是在ORACLE的数据字典中修改了分区和表的结构。数据并未发生任何修改，因此速度很快.对于大表来说，非常高效！如下测试案例所示：

SQL> create table test.big_table

  2  as

  3  select object_id, object_name from dba_objects;

Table created.

SQL> 

SQL> 

SQL> create table test1.big_table

  2  (     object_id    number,

  3        object_name  varchar2(128) 

  4  )

  5  partition by range( object_id)

  6  (

  7     partition big_table_par values less than(maxvalue)

  8  );

Table created.

SQL> alter table test1.big_table exchange partition big_table_par

  2  with table test.big_table;

Table altered.

SQL> select count(*) from test1.big_table;

  COUNT(*)

----------

     72329

SQL> select count(*) from test.big_table;

  COUNT(*)

----------

         0

SQL> 

如上所示，我们假设test.big_table是一个非常大的表，那么使用exchange partition就能快速、高效地将一个大表修改Schema,唯一不足的是，需要将普通表修改为分区表，当然，很多时候，大表很可能已经是分区表，使用这种方式不会有任何修改。另外，我们上面都是测试普通表，其实如果是分区表，使用exchange partition则是最佳选择！

参考资料：

https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:752030266230