概述
移动一张表实际上是一个重组过程，数据库会将原来的数据复制到新的地方。但是如果你发现这个表在移动后性能下降了，可能是你的索引没有重建。本文将指导您找到依赖索引并重建它们。
将表从示例移动到用户
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
查看哪些索引取决于此表
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.
如您所见，所有依赖索引都是UNUSABLE。这意味着，数据库不会自动重建它们。你必须自己做。
编写所有重建语句，然后执行它们
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间的索引。
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.
请注意，我们在新表空间USERS中重建索引。也就是说，对于索引，REBUILD相当于表中的MOVE
重建后检查状态
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.
所有索引都变为VALID，表明所重建的索引有效。
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