ORACLE 表移動後必須做的事
阿新 • • 發佈：2022-05-25
概述
移動一張表實際上是一個重組過程，資料庫會將原來的資料複製到新的地方。但是如果你發現這個表在移動後效能下降了，可能是你的索引沒有重建。本文將指導您找到依賴索引並重建它們。
將表從示例移動到使用者
SQL> select tablespace_name from dba_tables where owner = 'HR' and table_name = 'EMPLOYEES';
TABLESPACE_NAME
------------------------------
EXAMPLE
SQL> alter table hr.employees move tablespace users;
Table altered.
SQL> select tablespace_name from dba_tables where owner = 'HR' and table_name = 'EMPLOYEES';
TABLESPACE_NAME
------------------------------
USERS
檢視哪些索引取決於此表
SQL> column index_name format a30;
SQL> column tablespace_name format a30;
SQL> column status format a10;
SQL> select index_name, tablespace_name, status from dba_indexes where owner = 'HR' and table_name = 'EMPLOYEES';
INDEX_NAME TABLESPACE_NAME STATUS
------------------------------ ------------------------------ ----------
EMP_JOB_IX EXAMPLE UNUSABLE
EMP_DEPARTMENT_IX EXAMPLE UNUSABLE
EMP_MANAGER_IX EXAMPLE UNUSABLE
EMP_NAME_IX EXAMPLE UNUSABLE
EMP_EMAIL_UK EXAMPLE UNUSABLE
EMP_EMP_ID_PK EXAMPLE UNUSABLE
6 rows selected.
如您所見，所有依賴索引都是UNUSABLE。這意味著，資料庫不會自動重建它們。你必須自己做
編寫所有重建語句，然後執行它們
SQL> select 'alter index ' || owner || '.' ||index_name || ' rebuild tablespace users;' as SQL_TO_BE_EXECUTED from dba_indexes where owner = 'HR' and table_name = 'EMPLOYEES';
SQL_TO_BE_EXECUTED
--------------------------------------------------------------------------------
alter index EMP_JOB_IX rebuild tablespace users;
alter index EMP_DEPARTMENT_IX rebuild tablespace users;
alter index EMP_MANAGER_IX rebuild tablespace users;
alter index EMP_NAME_IX rebuild tablespace users;
alter index EMP_EMAIL_UK rebuild tablespace users;
alter index EMP_EMP_ID_PK rebuild tablespace users;
6 rows selected.
或者您可以重建原始表空間的索引。
SQL> select 'alter index ' || owner || '.' ||index_name || ' rebuild tablespace ' || tablespace_name || ';' as SQL_TO_BE_EXECUTED from dba_indexes where owner = 'HR' and table_name = 'EMPLOYEES';
SQL_TO_BE_EXECUTED
--------------------------------------------------------------------------------
alter index HR.EMP_DEPARTMENT_IX rebuild tablespace EXAMPLE;
alter index HR.EMP_NAME_IX rebuild tablespace EXAMPLE;
alter index HR.EMP_MANAGER_IX rebuild tablespace EXAMPLE;
alter index HR.EMP_EMP_ID_PK rebuild tablespace EXAMPLE;
alter index HR.EMP_EMAIL_UK rebuild tablespace EXAMPLE;
alter index HR.EMP_JOB_IX rebuild tablespace EXAMPLE;
6 rows selected.
請注意，我們在新表空間USERS中重建索引。也就是說，對於索引，REBUILD相當於表中的MOVE
重建後檢查狀態
SQL> select index_name, tablespace_name, status from dba_indexes where owner = 'HR' and table_name = 'EMPLOYEES';
INDEX_NAME TABLESPACE_NAME STATUS
------------------------------ ------------------------------ ----------
EMP_JOB_IX USERS VALID
EMP_DEPARTMENT_IX USERS VALID
EMP_MANAGER_IX USERS VALID
EMP_NAME_IX USERS VALID
EMP_EMAIL_UK USERS VALID
EMP_EMP_ID_PK USERS VALID
6 rows selected.
所有索引都變為VALID，表明所重建的索引有效。