【TEMPORARY TABLE】Oracle臨時(shí)表使用注意事項(xiàng)

發(fā)布時(shí)間：2020-08-10 02:48:15 來源：ITPUB博客閱讀：372 作者：eddy0lion 欄目：建站服務(wù)器

此文將給出在使用Oracle臨時(shí)表的過程中需要注意的事項(xiàng)，并對(duì)這些特點(diǎn)進(jìn)行驗(yàn)證。
①臨時(shí)表不支持物化視圖
②可以在臨時(shí)表上創(chuàng)建索引
③可以基于臨時(shí)表創(chuàng)建視圖
④臨時(shí)表結(jié)構(gòu)可被導(dǎo)出，但內(nèi)容不可以被導(dǎo)出
⑤臨時(shí)表通常是創(chuàng)建在用戶的臨時(shí)表空間中的，不同用戶可以有自己的獨(dú)立的臨時(shí)表空間
⑥不同的session不可以互相訪問對(duì)方的臨時(shí)表數(shù)據(jù)
⑦臨時(shí)表數(shù)據(jù)將不會(huì)上DML（Data Manipulation Language）鎖

1.臨時(shí)表不支持物化視圖
1）環(huán)境準(zhǔn)備
（1）創(chuàng)建基于會(huì)話的臨時(shí)表
sec@ora10g> create global temporary table t_temp_session (x int) on commit preserve rows;

Table created.

sec@ora10g> col TABLE_NAME for a30
sec@ora10g> col TEMPORARY for a10
sec@ora10g> select TABLE_NAME,TEMPORARY from user_tables where table_name = 'T_TEMP_SESSION';

TABLE_NAME                     TEMPORARY
------------------------------ ----------
T_TEMP_SESSION                 Y

（2）初始化兩條數(shù)據(jù)
sec@ora10g> insert into t_temp_session values (1);

1 row created.

sec@ora10g> insert into t_temp_session values (2);

1 row created.

sec@ora10g> commit;

Commit complete.

sec@ora10g> select * from t_temp_session;

         X
----------
         1
         2

（3）在臨時(shí)表T_TEMP_SESSION上添加主鍵
sec@ora10g> alter table T_TEMP_SESSION add constraint PK_T_TEMP_SESSION primary key(x);

Table altered.

2）在臨時(shí)表T_TEMP_SESSION上創(chuàng)建物化視圖
（1）創(chuàng)建物化視圖日志日志
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

可見，在創(chuàng)建物化視圖時(shí)便提示，臨時(shí)表上無(wú)法創(chuàng)建物化視圖日志。

（2）創(chuàng)建物化視圖
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

由于物化視圖日志沒有創(chuàng)建成功，因此顯然物化視圖亦無(wú)法創(chuàng)建。

2.在臨時(shí)表上創(chuàng)建索引
sec@ora10g> create index i_t_temp_session on t_temp_session (x);

Index created.

臨時(shí)表上索引創(chuàng)建成功。

3.基于臨時(shí)表創(chuàng)建視圖
sec@ora10g> create view v_t_temp_session as select * from t_temp_session where x<100;

View created.

基于臨時(shí)表的視圖創(chuàng)建成功。

4.臨時(shí)表結(jié)構(gòu)可被導(dǎo)出，但內(nèi)容不可以被導(dǎo)出
1）使用exp工具備份臨時(shí)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.

可見在備份過程中，沒有顯示有數(shù)據(jù)被導(dǎo)出。

2）使用imp工具的show選項(xiàng)查看備份介質(zhì)中的SQL內(nèi)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.

這里體現(xiàn)了創(chuàng)建臨時(shí)表和索引的語(yǔ)句，因此臨時(shí)表的結(jié)構(gòu)數(shù)據(jù)是可以被導(dǎo)出的。

3）嘗試導(dǎo)入數(shù)據(jù)
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.

依然顯示沒有記錄被導(dǎo)入。

5.查看臨時(shí)表空間的使用情況
可以通過查詢V$SORT_USAGE視圖獲得相關(guān)信息。
sec@ora10g> select username,tablespace,session_num sid,sqladdr,sqlhash,segtype,extents,blocks from v$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

可見SEC用戶中創(chuàng)建的臨時(shí)表以及其上的索引均存放在TEMP臨時(shí)表空間中。
在創(chuàng)建用戶的時(shí)候，可以指定用戶的默認(rèn)臨時(shí)表空間，這樣不同用戶在創(chuàng)建臨時(shí)表的時(shí)候便可以使用各自的臨時(shí)表空間，互不干擾。

6.不同的session不可以互相訪問對(duì)方的臨時(shí)表數(shù)據(jù)
1）在第一個(gè)session中查看臨時(shí)表數(shù)據(jù)
sec@ora10g> select * from t_temp_session;

         X
----------
         1
         2

此數(shù)據(jù)為初始化環(huán)境時(shí)候插入的數(shù)據(jù)。

2）在單獨(dú)開啟一個(gè)session，查看臨時(shí)表數(shù)據(jù)。
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

說明不同的session擁有各自獨(dú)立的臨時(shí)表操作特點(diǎn)，不同的session之間是不能互相訪問數(shù)據(jù)。

7.臨時(shí)表數(shù)據(jù)將不會(huì)上DML（Data Manipulation Language）鎖
1）在新session中查看SEC用戶下鎖信息
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

不存在任何鎖信息。

2）向臨時(shí)表中插入數(shù)據(jù)，查看鎖信息
（1）插入數(shù)據(jù)
sec@ora10g> insert into t_temp_session values (1);

1 row created.

（2）查看鎖信息
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

此時(shí)出現(xiàn)TO和TX類型鎖。

（3）提交數(shù)據(jù)后再次查看鎖信息
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

事務(wù)所TX被釋放。TO鎖保留。

3）測(cè)試更新數(shù)據(jù)場(chǎng)景下鎖信息變化
（1）更新臨時(shí)表數(shù)據(jù)
sec@ora10g> update t_temp_session set x=100;

1 row updated.

（2）鎖信息如下
                               lock                                lock
USERNAME        SID    SERIAL# type           id1         id2      mode
-------- ---------- ---------- ------ ----------- ----------- ---------
SEC             142        425 TO           12125           1         3
SEC             142        425 TX          524317         464         6

（3）提交數(shù)據(jù)
sec@ora10g> commit;

Commit complete.

（4）鎖信息情況
                               lock                                lock
USERNAME        SID    SERIAL# type           id1         id2      mode
-------- ---------- ---------- ------ ----------- ----------- ---------
SEC             142        425 TO           12125           1         3

4）測(cè)試刪除數(shù)據(jù)場(chǎng)景下鎖信息變化
（1）刪除臨時(shí)表數(shù)據(jù)
sec@ora10g> delete from t_temp_session;

1 row deleted.

（2）查看鎖信息
                               lock                                lock
USERNAME        SID    SERIAL# type           id1         id2      mode
-------- ---------- ---------- ------ ----------- ----------- ---------
SEC             142        425 TO           12125           1         3
SEC             142        425 TX          327713         462         6

（3）提交數(shù)據(jù)
sec@ora10g> commit;

Commit complete.

（4）鎖信息情況
                               lock                                lock
USERNAME        SID    SERIAL# type           id1         id2      mode
-------- ---------- ---------- ------ ----------- ----------- ---------
SEC             142        425 TO           12125           1         3

5）總結(jié)
在臨時(shí)表上的增刪改等DML操作都會(huì)產(chǎn)生TO鎖和TX事務(wù)所。TO鎖會(huì)從插入數(shù)據(jù)開始一直存在。
但整個(gè)過程中都不會(huì)產(chǎn)生DML的TM級(jí)別鎖。

8.小結(jié)
本文就臨時(shí)表使用過程中常見的問題和特點(diǎn)進(jìn)行了介紹。臨時(shí)表作為Oracle的數(shù)據(jù)庫(kù)對(duì)象，如果能夠在理解這些特性基礎(chǔ)上加以利用將會(huì)極大地改善系統(tǒng)性能。

Good luck.

secooler
11.06.29

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【TEMPORARY TABLE】Oracle臨時(shí)表使用注意事項(xiàng)

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