一、创建索引注意事项

1、预估索引大小

2、查看索引表空间可用空间大小

3、查看临时表空间大小

4、业务空闲期创建

5、可以考虑在线、并行、nologging模式

二、预估索引方法

操作步骤如下：

sql> explain plan for create index idx_object_id on tt(object_id) ;

Explained.

sql> set lines 200 pages 1000

sql> select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT

-------------------------------------------------------------------------------------------------------------------------------

Plan hash value: 3757763116

----------------------------------------------------------------------------------------

| Id | Operation | Name | Rows | Bytes | Cost (%cpu)| Time |

| 0 | CREATE INDEX STATEMENT | | 2762K| 13M| 22958 (1)| 00:04:36 |

| 1 | INDEX BUILD NON UNIQUE| IDX_OBJECT_ID | | | | |

| 2 | SORT CREATE INDEX | | 2762K| 13M| | |

| 3 | TABLE ACCESS FULL | TT | 2762K| 13M| 21560 (1)| 00:04:19 |

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Note

-----

- estimated index size: 67M bytes

14 rows selected.

Elapsed: 00:00:00.01

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