Oracle線上重定義(online redefinition)--將普通表改為分割槽表
使用Oracle的線上重定義技術，可以將Oracle的普通表改為分割槽表。操作如下：
STEP1
：測試表是否可以線上重定義，這裡以unixdev資料庫的LIJIAMAN.BSTEST為例
EXEC DBMS_REDEFINITION.CAN_REDEF_TABLE('LIJIAMAN','BSTEST', DBMS_REDEFINITION.CONS_USE_PK);
如果表上沒有主鍵，則會報錯：
SQL> exec dbms_redefinition.start_redef_table('LIJIAMAN', 'BSTEST', 'BSTEST_TMP');
ORA-12089: 不能聯機重新定義無主鍵的表 "LIJIAMAN"."BSTEST"
ORA-06512: 在 "SYS.DBMS_REDEFINITION", line 56
ORA-06512: 在 "SYS.DBMS_REDEFINITION", line 1498
ORA-06512: 在 line 1
STEP2 ：建立中間表
除了表名稱外，該中間表的形式需要與我們最終的分割槽表的形式一模一樣，如列名，列的資料型別、分割槽欄位，分割槽方法等。
create table BSTEST_tmp
( TIMEKEY VARCHAR2(40),
ITEMNAME VARCHAR2(40),
SITENAME VARCHAR2(40),
SITEVALUE VARCHAR2(40)
)
partition by range (timekey)
( partition part_201711 values less than('201712010000000000000'),
partition part_201712 values less than('201801010000000000000'),
partition part_201801 values less than('201802010000000000000'),
partition part_201802 values less than('201803010000000000000'),
partition part_201803 values less than('201804010000000000000'),
partition part_201804 values less than('201805010000000000000'),
partition part_201805 values less than('201806010000000000000'),
partition part_201806 values less than('201807010000000000000'),
partition part_201807 values less than('201808010000000000000'),
partition part_201808 values less than('201809010000000000000'),
partition part_201809 values less than('201810010000000000000'),
partition part_201810 values less than('201811010000000000000'),
partition part_201811 values less than('201812010000000000000'),
partition part_201812 values less than('201901010000000000000'),
partition part_201901 values less than('201902010000000000000'),
partition part_201902 values less than('201903010000000000000'),
partition part_201903 values less than('201904010000000000000'),
partition part_201904 values less than('201905010000000000000'),
partition part_201905 values less than('201906010000000000000'),
partition part_201906 values less than('201907010000000000000'),
partition part_201907 values less than('201908010000000000000'),
partition part_201908 values less than('201909010000000000000'),
partition part_201909 values less than('201910010000000000000'),
partition part_201910 values less than('201911010000000000000'),
partition part_201911 values less than('201912010000000000000'),
partition part_201912 values less than('202001010000000000000'),
partition part_202001 values less than('202002010000000000000'),
partition part_202002 values less than('202003010000000000000'),
partition part_202003 values less than('202004010000000000000'),
partition part_202004 values less than('202005010000000000000'),
partition part_max values less than(maxvalue)
);
STEP3 ：執行線上重定義
exec dbms_redefinition.start_redef_table('LIJIAMAN', 'BSTEST', 'BSTEST_TMP');
備註：該步驟執行時間較長，3.7GB的表執行了60s
STEP4 ：將中間表的內容與資料來源同步
execute dbms_redefinition.sync_interim_table('LIJIAMAN', 'BSTEST', 'BSTEST_TMP');
STEP5 ：結束線上重定義
exec dbms_redefinition.finish_redef_table('LIJIAMAN', 'BSTEST', 'BSTEST_TMP');
STEP6 ：建立index、建立約束，兩種方法建立速度差不多
alter session set db_file_multiblock_read_count=128; alter table BSTEST add constraint BSPANELPROCESSDATAITEM_PKS primary key(timekey,itemname,sitename) using index local tablespace users;
STEP7 ：收集統計資訊
exec dbms_stats.gather_table_stats(ownname=>'LIJIAMAN', tabname=>'BSTEST', method_opt=> 'FOR ALL INDEXED COLUMNS', estimate_percent => 10, cascade=>true);
備註：該步驟執行時間較長，3.7GB的表執行了36s，如果嫌慢，可以並行收集
STEP8 ：確認無誤之後，刪除STEP2建立的中間表
drop table BSTEST_TMP;
如果要了解線上重定義的詳細用法及使用注意事項，可參閱官方文件：
1. https://docs.oracle.com/cd/E11882_01/server.112/e25494/tables.htm#ADMIN11677
2. How To Partition Existing Table Using DBMS_REDEFINITION (文件 ID 472449.1)