上添加主键

sec@ora10g> alter table T_TEMP_SESSION add constraint PK_T_TEMP_SESSION primary key(x);

Table altered.

2)在临时表T_TEMP_SESSION上创建物化视图

(1)创建物化视图日志日志

sec@ora10g> create materialized view log on T_TEMP_SESSION with sequence, rowid (x) including new values;

create materialized view log on T_TEMP_SESSION with sequence, rowid (x) including new values

*

ERROR at line 1:

ORA-14451: unsupported feature with temporary table

可见，在创建物化视图时便提示，临时表上无法创建物化视图日志。

(2)创建物化视图

sec@ora10g> create materialized view mv_T_TEMP_SESSION build immediate refresh fast on commit enable query rewrite as select * from T_TEMP_SESSION;

create materialized view mv_T_TEMP_SESSION build immediate refresh fast on commit enable query rewrite as select * from T_TEMP_SESSION

*

ERROR at line 1:

ORA-23413: table "SEC"."T_TEMP_SESSION" does not have a materialized view log

由于物化视图日志没有创建成功，因此显然物化视图亦无法创建。

2.在临时表上创建索引

sec@ora10g> create index i_t_temp_session on t_temp_session (x);

Index created.

临时表上索引创建成功。

3.基于临时表创建视图

sec@ora10g> create view v_t_temp_session as select * from t_temp_session where x<100;

View created.

基于临时表的视图创建成功。

4.临时表结构可被导出，但内容不可以被导出

1)使用exp工具备份临时表

ora10g@secdb /home/oracle$ exp sec/sec file=t_temp_session.dmp log=t_temp_session.log tables=t_temp_session

Export: Release 10.2.0.1.0 - Production on Wed Jun 29 22:06:43 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production

With the Partitioning, OLAP and Data Mining options

Export done in WE8ISO8859P1 character set and AL16UTF16 NCHAR character set

About to export specified tables via Conventional Path ...

. . exporting table                 T_TEMP_SESSION

Export terminated successfully without warnings.

可见在备份过程中，没有显示有数据被导出。

2)使用imp工具的show选项查看备份介质中的SQL内容

ora10g@secdb /home/oracle$ imp sec/sec file=t_temp_session.dmp full=y show=y

Import: Release 10.2.0.1.0 - Production on Wed Jun 29 22:06:57 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production

With the Partitioning, OLAP and Data Mining options

Export file created by EXPORT:V10.02.01 via conventional path

import done in WE8ISO8859P1 character set and AL16UTF16 NCHAR character set

. importing SEC's objects into SEC

. importing SEC's objects into SEC

"CREATE GLOBAL TEMPORARY TABLE "T_TEMP_SESSION" ("X" NUMBER(*,0)) ON COMMIT "

"PRESERVE ROWS "

"CREATE INDEX "I_T_TEMP_SESSION" ON "T_TEMP_SESSION" ("X" ) "

Import terminated successfully without warnings.

这里体现了创建临时表和索引的语句，因此临时表的结构数据是可以被导出的。

3)尝试导入数据

ora10g@secdb /home/oracle$ imp sec/sec file=t_temp_session.dmp full=y ignore=y

Import: Release 10.2.0.1.0 - Production on Wed Jun 29 22:07:16 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production

With the Partitioning, OLAP and Data Mining options

Export file created by EXPORT:V10.02.01 via conventional path

import done in WE8ISO8859P1 character set and AL16UTF16 NCHAR character set

. importing SEC's objects into SEC

. importing SEC's objects into SEC

Import terminated successfully without warnings.

依然显示没有记录被导入。

5.查看临时表空间的使用情况

可以通过查询V$SORT_USAGE视图获得相关信息。

sec@ora10g> select username,tablespace,session_num sid,sqladdr,sqlhash,segtype,extents,blocks from v$sort_usage;

USERNAME TABLESPACE     SID SQLADDR     SQLHASH SEGTYPE EXTENTS  BLOCKS

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

SEC      TEMP           370 389AEC58 1029988163 DATA          1     128

SEC      TEMP           370 389AEC58 1029988163 INDEX         1     128

可见SEC用户中创建的临时表以及其上的索引均存放在TEMP临时表空间中。

在创建用户的时候，可以指定用户的默认临时表空间，这样不同用户在创建临时表的时候便可以使用各自的临时表空间，互不干扰。

6.不同的session不可以互相访问对方的临时表数据

1)在第一个session中查看临时表数据

sec@ora10g> select * from t_temp_session;

X

----------

1

2

此数据为初始化环境时候插入的数据。

2)在单独开启一个session，查看临时表数据。

ora10g@secdb /home/oracle$ sqlplus sec/sec

SQL*Plus: Release 10.2.0.1.0 - Production on Wed Jun 29 22:30:05 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:

Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production

With the Partitioning, OLAP and Data Mining options

sec@ora10g> select * from t_temp_session;

no rows selected

说明不同的session拥有各自独立的临时表操作特点，不同的session之间是不能互相访问数据。

7.临时表数据将不会上DML(Data Manipulation Language)锁

1)在新session中查看SEC用户下锁信息

sec@ora10g> col username for a8

sec@ora10g> select

2       b.username,

3       a.sid,

4       b.serial#,

5       a.type "lock type",

6       a.id1,

7       a.id2,

8       a.lmode

9  from v$lock a, v$session b

10  where a.sid=b.sid and b.username = 'SEC'

11  order by username,a.sid,serial#,a.type;

no rows selected

不存在任何锁信息。

2)向临时表中插入数据，查看锁信息

(1)插入数据

sec@ora10g> insert into t_temp_session values (1);

1 row created.

(2)查看锁信息

sec@ora10g> select

2       b.username,

3       a.sid,

4       b.serial#,

5       a.type "lock type",

6       a.id1,

7       a.id2,

8       a.lmode

9  from v$lock a, v$session b

10  where a.sid=b.sid and b.username = 'SEC'

11  order by username,a.sid,serial#,a.type;

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

SEC             142        425 TX           65554         446         6

此时出现TO和TX类型锁。

(3)提交数据后再次查看锁信息

sec@ora10g> commit;

Commit complete.

sec@ora10g> select

2       b.username,

3       a.sid,

4       b.serial#,

5       a.type "lock type",

6       a.id1,

7       a.id2,

8       a.lmode

9  from v$lock a, v$session b

10  where a.sid=b.sid and b.username = 'SEC'

11  order by username,a.sid,serial#,a.type;

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

事务所TX被释放。TO锁保留。

3)测试更新数据场景下锁信息变化

(1)更新临时表数据

sec@ora10g> update t_temp_session set x=100;

1 row updated.

(2)锁信息如下

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

SEC             142        425 TX          524317         464         6

(3)提交数据

sec@ora10g> commit;

Commit complete.

(4)锁信息情况

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

4)测试删除数据场景下锁信息变化

(1)删除临时表数据

sec@ora10g> delete from t_temp_session;

1 row deleted.

(2)查看锁信息

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

SEC             142        425 TX          327713         462         6

(3)提交数据

sec@ora10g> commit;

Commit complete.

(4)锁信息情况

lock                                lock

USERNAME        SID    SERIAL# type           id1         id2      mode

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

SEC             142        425 TO           12125           1         3

5)总结

在临时表上的增删改等DML操作都会产生TO锁和TX事务所。TO锁会从插入数据开始一直存在。

但整个过程中都不会产生DML的TM级别锁。

8.小结

本文就临时表使用过程中常见的问题和特点进行了介绍。临时表作为Oracle的数据库对象，如果能够在理解这些特性基础上加以利用将会极大地改善系统性能。

Good luck.

secooler

11.06.29

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