Oracle Online Redefinition在线重定义（下）
在之前的文章中，我們看到了如何處理單表在線重定義過程。本篇我們來看一下如何進(jìn)行關(guān)聯(lián)表的重定義過程。
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4、外鍵關(guān)系表重定義
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我們先創(chuàng)建出實(shí)驗(yàn)數(shù)據(jù)表。
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SQL> create table t_master as select owner, table_name, tablespace_name, status from dba_tables where 1=0;
Table created
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SQL> alter table t_master add constraint pk_t_master primary key (owner, table_name);
Table altered
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Executed in 0.125 seconds
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SQL> create table t_slave as select owner, table_name, column_name from dba_tab_columns where 1=0;
Table created
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SQL> alter table T_SLAVE
? 2??? add constraint pk_t_slave primary key (OWNER, TABLE_NAME, COLUMN_NAME);
Table altered
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Executed in 0.422 seconds
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T_MASTER和T_SLAVE構(gòu)成主子表關(guān)系，插入數(shù)據(jù)。
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SQL> insert into t_master select owner, table_name, tablespace_name, status from dba_tables;
2841 rows inserted
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Executed in 0.157 seconds
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SQL> commit;
Commit complete
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Executed in 0 seconds
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SQL> insert into t_slave select owner, table_name, column_name from dba_tab_cols where (owner, table_name) in (select owner, table_name from dba_tables);
32388 rows inserted
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Executed in 2.328 seconds
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SQL> commit;
Commit complete
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Executed in 0 seconds
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SQL> alter table T_SLAVE
? 2??? add constraint fk_t_slave_master foreign key (OWNER, TABLE_NAME)
? 3??? references t_master (OWNER, TABLE_NAME);
Table altered
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Executed in 0.266 seconds
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創(chuàng)建interim中間表對象，主要目標(biāo)是將數(shù)據(jù)表按照owner進(jìn)行分區(qū)，轉(zhuǎn)化為分區(qū)表。
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SQL> create table t_master_interim
? 2? (owner varchar2(30),
? 3?? TABLE_NAME????? VARCHAR2(30),
? 4?? TABLESPACE_NAME VARCHAR2(30),
? 5?? STATUS????????? VARCHAR2(8)
? 6? )
? 7? partition by list(owner)
? 8? (
??9???? partition p1 values ('SYS'),
?10???? partition p2 values (default)
?11? )
?12? ;
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Table created
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Executed in 0.156 seconds
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SQL> create table t_slave_interim
? 2? (owner varchar2(30),
? 3?? table_name varchar2(30),
? 4?? column_name varchar2(30)
? 5? )
? 6? partition by list(owner)
? 7? (
? 8???? partition p1 values ('SYS'),
? 9???? partition p2 values (default)
?10? )
?11? ;
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Table created
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Executed in 0.032 seconds
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進(jìn)入正式的重定義流程。這個(gè)過程，如果處于安全和順序關(guān)系看，應(yīng)該是先子表后主表似乎好一點(diǎn)。筆者選擇了先主表后子表的方法。
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--判斷是否可以進(jìn)行在線重定義過程；
SQL> set serveroutput on;
SQL> exec dbms_redefinition.can_redef_table('SCOTT','T_MASTER',options_flag => dbms_redefinition.cons_use_pk);
PL/SQL procedure successfully completed
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Executed in 0.172 seconds
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SQL> exec dbms_redefinition.can_redef_table('SCOTT','T_SLAVE',options_flag => dbms_redefinition.cons_use_pk);
PL/SQL procedure successfully completed
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Executed in 0.015 seconds
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T_MASTER表進(jìn)行重定義過程。
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SQL> exec dbms_redefinition.start_redef_table('SCOTT','T_MASTER','T_MASTER_INTERIM',col_mapping => 'owner owner, table_name table_name, tablespace_name tablespace_name, status status',options_flag => dbms_redefinition.cons_use_pk);
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PL/SQL procedure successfully completed
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Executed in 1.125 seconds
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SQL> exec dbms_redefinition.sync_interim_table('SCOTT','T_MASTER','T_MASTER_INTERIM');
PL/SQL procedure successfully completed
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Executed in 0.047 seconds
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SQL>
SQL> set serveroutput on;
SQL> declare
? 2??? error_count number:=0;
? 3? begin
? 4??? dbms_redefinition.copy_table_dependents(uname => 'SCOTT',orig_table => 'T_MASTER',
? 5??????????????????????????????????????????? int_table => 'T_MASTER_INTERIM',
? 6??????????????????????????????????????????? copy_indexes => dbms_redefinition.cons_orig_params,
? 7??????????????????????????????????????????? num_errors => error_count);
? 8??? dbms_output.put_line(to_char(error_count));
? 9? end;
?10? /
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0
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PL/SQL procedure successfully completed
Executed in 6.766 seconds
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SQL> exec dbms_redefinition.finish_redef_table('SCOTT','T_MASTER','T_MASTER_INTERIM');
PL/SQL procedure successfully completed
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Executed in 1.75 seconds
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進(jìn)行T_SLAVE表重定義過程。
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SQL> exec dbms_redefinition.start_redef_table('SCOTT','T_SLAVE','T_SLAVE_INTERIM',col_mapping => 'owner owner, table_name table_name, column_name column_name',options_flag => dbms_redefinition.cons_use_pk);
PL/SQL procedure successfully completed
Executed in 1.484 seconds
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SQL> exec dbms_redefinition.sync_interim_table('SCOTT','T_SLAVE','T_SLAVE_INTERIM');
PL/SQL procedure successfully completed
Executed in 0.047 seconds
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SQL>
SQL> set serveroutput on;
SQL> declare
? 2??? error_count number:=0;
? 3? begin
? 4??? dbms_redefinition.copy_table_dependents(uname => 'SCOTT',orig_table => 'T_SLAVE',
? 5??????????????????????????????????????????? int_table => 'T_SLAVE_INTERIM',
? 6??????????????????????????????????????????? copy_indexes => dbms_redefinition.cons_orig_params,
? 7??????????????????????????????????????????? num_errors => error_count);
? 8??? dbms_output.put_line(to_char(error_count));
? 9? end;
?10? /
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0
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PL/SQL procedure successfully completed
Executed in 6.718 seconds
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SQL> exec dbms_redefinition.finish_redef_table('SCOTT','T_SLAVE','T_SLAVE_INTERIM');
PL/SQL procedure successfully completed
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Executed in 1.75 seconds
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最后，我們檢查處理結(jié)果。
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--分區(qū)處理成功；
SQL> select table_name, partition_name from dba_tab_partitions where table_owner='SCOTT' and table_name in ('T_MASTER','T_SLAVE');
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TABLE_NAME???????????????????? PARTITION_NAME
------------------------------ ------------------------------
T_MASTER??????????????????? ???P1
T_MASTER?????????????????????? P2
T_SLAVE??????????????????????? P1
T_SLAVE??????????????????????? P2
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Executed in 0.031 seconds
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約束中存在一些需要額外處理的地方。
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SQL> select constraint_name, constraint_type, R_CONSTRAINT_NAME from dba_constraints where wner='SCOTT' and table_name in ('T_MASTER','T_SLAVE');
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CONSTRAINT_NAME??????????????? CONSTRAINT_TYPE R_CONSTRAINT_NAME
------------------------------ --------------- ------------------------------
TMP$$_FK_T_SLAVE_MASTER0?????? R?????????????? TMP$$_PK_T_MASTER0
SYS_C0011276?????????????????? C??????????????
SYS_C0011275?????????????????? C??????????????
SYS_C0011274?????????????????? C??????????????
PK_T_SLAVE???????????????????? P??????????????
FK_T_SLAVE_MASTER????????????? R?????????????? PK_T_MASTER
SYS_C0011272?????????????????? C??????????????
SYS_C0011271?????????????????? C??????????????
PK_T_MASTER??????????????????? P??????????????
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9 rows selected
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Executed in 0.141 seconds
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由于是分別進(jìn)行的重定義動(dòng)作，中間可能有關(guān)聯(lián)裹挾的情況，所以需要額外進(jìn)行一些處理。主要目標(biāo)是將Interim數(shù)據(jù)表刪除掉。
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SQL> drop table t_slave_interim;
Table dropped
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Executed in 0.438 seconds
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SQL> alter table t_slave drop constraint "TMP$$_FK_T_SLAVE_MASTER0";
Table altered
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Executed in 0.031 seconds
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SQL> drop table t_master_interim purge;
Table dropped
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Executed in 0.094 seconds
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檢查約束情況。
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SQL> select constraint_name, constraint_type, R_CONSTRAINT_NAME from dba_constraints where wner='SCOTT' and table_name in ('T_MASTER','T_SLAVE');
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CONSTRAINT_NAME??????????????? CONSTRAINT_TYPE R_CONSTRAINT_NAME
------------------------------ --------------- ------------------------------
PK_T_MASTER??????????????????? P??????????????
PK_T_SLAVE???????????????????? P??????????????
FK_T_SLAVE_MASTER????????????? R?????????????? PK_T_MASTER
SYS_C0011271?????????? ????????C??????????????
SYS_C0011272?????????????????? C??????????????
SYS_C0011274?????????????????? C??????????????
SYS_C0011275?????????????????? C??????????????
SYS_C0011276?????????????????? C??????????????
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8 rows selected
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Executed in 0.125 seconds
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重定義成功。
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5、結(jié)論和討論
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Oracle在線重定義是一種非常強(qiáng)大的定義工具。這個(gè)系列只是介紹了該特性中最常用的一些流程和方法。其他一些諸如register對象和重命名的方法，在一些特定場合下有比較好的使用空間。
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應(yīng)該說，Oracle在線重定義是一種平滑性能、減少鎖定、提高系統(tǒng)整體可用性的解決方案。從操作時(shí)間和空間消耗上，在線重定義并不具有很高的優(yōu)勢。對于7*24小時(shí)的系統(tǒng)，該特性是一種不錯(cuò)的選擇。
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