1.創建模擬表
SQL>
select
* from
v$version;BANNER--------------------------------------------------------------------------------Oracle
Database
11g Enterprise Edition Release 11.2.0.3.0 - 64bit ProductionPL/SQL
Release 11.2.0.3.0 - ProductionCORE
11.2.0.3.0 ProductionTNS
for
Linux: Version 11.2.0.3.0 - ProductionNLSRTL
Version 11.2.0.3.0 - ProductionSQL>
create
table
chf.t_xifenfei_move 2
as 3
select
* from
dba_objects;Table
created.SQL>
select
count(*)
from
chf.t_xifenfei_move; COUNT(*)---------- 73585SQL>
create
table
chf.t_xifenfei_move 2
as 3
select
* from
dba_objects;Table
created.SQL>
select
count(*)
from
chf.t_xifenfei_move; COUNT(*)---------- 73585SQL>
DECLARE 2
i NUMBER; 3
BEGIN 4
FOR
i IN
1..100 LOOP 5
INSERT
INTO
chf.t_xifenfei_move 6
select
* from
dba_objects; 7
END
LOOP; 8
COMMIT; 9
END; 10
/PL/SQL
procedure
successfully completed.SQL>
exec
dbms_stats.gather_table_stats('CHF','T_XIFENFEI_MOVE');PL/SQL
procedure
successfully completed.SQL>
select
bytes from
dba_segments where
segment_name='T_XIFENFEI_MOVE'; BYTES---------- 872415232 |
2.測試move
2.1)執行move操作，記錄時間
SQL>
alter
system flush buffer_cache;System
altered.SQL>
SET
TIMING ON;
SQL>
alter
session set
events 2
'10046
trace name context forever,level 1';Session
altered.Elapsed:
00:00:00.00SQL>
ALTER
TABLE
CHF.T_XIFENFEI_MOVE MOVE
TABLESPACE USERS;Table
altered.Elapsed:
00:02:11.77SQL>
alter
session set
events 2
'10046
trace name context off';Session
altered.Elapsed:
00:00:00.04SQL>
select
d.value||'/'||lower(rtrim(i.instance,chr(0)))||'_ora_'||p.spid||'.trc'
trace_file_name from 2
(select
p.spid from
v$mystat m, v$session s,v$process p where
m.statistic# = 1 and
s.sid = m.sid and
p.addr = s.paddr ) p, 3
(select
t.instance from
v$thread t,v$parameter v where
v.name
= 'thread'
and(v.value
= 0 or
t.thread# = to_number(v.value))) i, 4
(select
value from
v$parameter where
name
= 'user_dump_dest')
d;TRACE_FILE_NAME--------------------------------------------------------------------------------/opt/oracle/diag/rdbms/chf/chf/trace/chf_ora_4765.trc |
從這裏可以看出，move操作執行了00:02:11.77
2.2)查看trace內容
[oracle@node1
~]$ tkprof /opt/oracle/diag/rdbms/chf/chf/trace/chf_ora_4765.trc
/tmp/xifenfei_move.txtTKPROF:
Release 11.2.0.3.0 - Development on Tue Jan 10 10:57:59 2012Copyright
(c) 1982, 2011, Oracle and/or
its affiliates. All rights reserved.********************************************************************************SQL
ID: c1yk5pv0v1wg1 Plan Hash: 2931676921ALTER
TABLE CHF.T_XIFENFEI_MOVE MOVE TABLESPACE USERScall
count cpu elapsed disk query current rows-------
------ -------- ---------- ---------- ---------- ---------- ----------Parse
1 0.00 0.05 7 8 0 0Execute
1 11.29 131.23 105584 106275 115654 7432085Fetch
0 0.00 0.00 0 0 0 0-------
------ -------- ---------- ---------- ---------- ---------- ----------total
2 11.30 131.29 105591 106283 115654 7432085Misses
in
library cache during parse: 1Optimizer
mode: ALL_ROWSParsing
user id:
SYSNumber
of plan statistics captured: 1Rows
(1st) Rows (avg) Rows (max) Row Source Operation----------
---------- ---------- --------------------------------------------------- 0
0 0 LOAD AS SELECT (cr=117799 pr=105602
pw=105585 time=131351005
us) 7432085
7432085 7432085 TABLE ACCESS FULL T_XIFENFEI_MOVE (cr=105591 pr=105586
pw=0 time=4735560
us cost=23453 size=720912245 card=7432085)******************************************************************************** |
從這裏可以看出執行move，其實本質是全表掃描表，然後append方式插入數據，而不是真的數據塊拷貝
3.測試CAST
3.1).CAST插入數據過程
SQL> alter system flush buffer_cache;
System altered.
SQL> SET TIMING ON;
SQL> alter session set events
2 ’10046 trace name context forever,level 1′;
Session altered.
Elapsed: 00:00:00.01
SQL> create table chf.t_xifenfei_move_new tablespace test_ocp
2 as
3 select * from chf.t_xifenfei_move;
Table created.
Elapsed: 00:01:59.22
SQL> alter session set events
2 ’10046 trace name context off’;
Session altered.
Elapsed: 00:00:00.00
SQL> select d.value||’/'||lower(rtrim(i.instance,chr(0)))||’_ora_’||p.spid||’.trc’ trace_file_name from
2 (select p.spid from v$mystat m, v$session s,v$process p where m.statistic# = 1 and s.sid = m.sid and p.addr = s.paddr ) p,
3 (select t.instance from v$thread t,v$parameter v where v.name = ‘thread’ and(v.value = 0 or t.thread# = to_number(v.value))) i,
4 (select value from v$parameter where name = ‘user_dump_dest’) d;
TRACE_FILE_NAME
——————————————————————————–
/opt/oracle/diag/rdbms/chf/chf/trace/chf_ora_5121.trc
從這裏看出cast操作用時:00:01:59.22，比move稍微少，但是cast要實現move完全的功能，還需要表重命名，表授權，編譯無效對象等。
3.2)查看trace內容
[oracle@node1
~]$ tkprof /opt/oracle/diag/rdbms/chf/chf/trace/chf_ora_5121.trc
/tmp/xifenfei_create.txtTKPROF:
Release 11.2.0.3.0 - Development on Tue Jan 10 11:08:19 2012Copyright
(c) 1982, 2011, Oracle and/or
its affiliates. All rights reserved.********************************************************************************create
table chf.t_xifenfei_move_new tablespace test_ocpasselect
* from chf.t_xifenfei_movecall
count cpu elapsed disk query current rows-------
------ -------- ---------- ---------- ---------- ---------- ----------Parse
1 0.00 0.02 1 4 0 0Execute
1 9.85 118.37 105587 106097 112387 7432085Fetch
0 0.00 0.00 0 0 0 0-------
------ -------- ---------- ---------- ---------- ---------- ----------total
2 9.85 118.40 105588 106101 112387 7432085Misses
in
library cache during parse: 1Optimizer
mode: ALL_ROWSParsing
user id:
SYSNumber
of plan statistics captured: 1Rows
(1st) Rows (avg) Rows (max) Row Source Operation----------
---------- ---------- --------------------------------------------------- 0
0 0 LOAD AS SELECT (cr=106631 pr=105592
pw=105585 time=118338607
us) 7432085
7432085 7432085 TABLE ACCESS FULL T_XIFENFEI_MOVE (cr=105591 pr=105586
pw=0 time=2935008
us cost=23453 size=720912245 card=7432085)******************************************************************************** |
通過這個可以看出，CAST其實本質也是全表掃描，然後append方式插入數據
4.比較move和cast
4.1)通過比較執行時間，cast稍微少，但是還有後續操作需要時間
4.2)通過比較執行計劃，兩者是一樣的
4.3)move操作在整個過程中都會鎖表,而cast不會鎖住原表(select+where可以減少停業務時間)
4.4)move操作會一次性處理好權限,plsql/view等有效,而cast在rename之後，相關對象可能需要重新編譯，重新授權等操作
4.5)cast操作index需要新建(create),而move操作index需要重建(rebuild)
4.6)cast完成後，需要對錶重命名，刪除原表操作操作，而這個操作move不用
5.選擇使用誰
5.1)如果停業務時間夠長，建議使用move操作
5.2)如果停業務時間不能太長，可以使用cast+where實現
5.3)如果數據庫版本>=10g,且表空間使用local管理，那麼可以考慮在不停業務的情況下使用shrink實現類此功能
至於MOVE和CAST在執行過程中，關於產生的redo和undo的比較，請見下篇:MOVE和CAST比較(續)
原文地址：http://www.xifenfei.com/2012/01/move%E5%92%8Ccast%E6%AF%94%E8%BE%83.html