數據大我有以下統計數據庫MySQL的指數大於存儲
Tables Data Index Total
11 579,6 MB 0,9 GB 1,5 GB
所以你可以看到指數接近2倍大。並且有一個約700萬行的表格佔據了至少99%。
我也有兩個指標非常相似
a) UNIQUE KEY `idx_customer_invoice` (`customer_id`,`invoice_no`),
b) KEY `idx_customer_invoice_order` (`customer_id`,`invoice_no`,`order_no`)
更新:這裏是全國最大的表的表定義(至少結構上)
CREATE TABLE `invoices` (
`id` int(10) unsigned NOT NULL auto_increment,
`customer_id` int(10) unsigned NOT NULL,
`order_no` varchar(10) default NULL,
`invoice_no` varchar(20) default NULL,
`customer_no` varchar(20) default NULL,
`name` varchar(45) NOT NULL default '',
`archived` tinyint(4) default NULL,
`invoiced` tinyint(4) default NULL,
`time` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
`group` int(11) default NULL,
`customer_group` int(11) default NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `idx_customer_invoice` (`customer_id`,`invoice_no`),
KEY `idx_time` (`time`),
KEY `idx_order` (`order_no`),
KEY `idx_customer_invoice_order` (`customer_id`,`invoice_no`,`order_no`)
) ENGINE=InnoDB AUTO_INCREMENT=9146048 DEFAULT CHARSET=latin1 |
更新2:
mysql> show indexes from invoices;
+----------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+----------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| invoices | 0 | PRIMARY | 1 | id | A | 7578066 | NULL | NULL | | BTREE | |
| invoices | 0 | idx_customer_invoice | 1 | customer_id | A | 17 | NULL | NULL | | BTREE | |
| invoices | 0 | idx_customer_invoice | 2 | invoice_no | A | 7578066 | NULL | NULL | YES | BTREE | |
| invoices | 1 | idx_time | 1 | time | A | 541290 | NULL | NULL | | BTREE | |
| invoices | 1 | idx_order | 1 | order_no | A | 6091 | NULL | NULL | YES | BTREE | |
| invoices | 1 | idx_customer_invoice_order | 1 | customer_id | A | 17 | NULL | NULL | | BTREE | |
| invoices | 1 | idx_customer_invoice_order | 2 | invoice_no | A | 7578066 | NULL | NULL | YES | BTREE | |
| invoices | 1 | idx_customer_invoice_order | 3 | order_no | A | 7578066 | NULL | NULL | YES | BTREE | |
+----------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
我的問題是:
- 有沒有辦法找到MySQL中未使用的索引?
- 是否有影響索引大小的常見錯誤?
- 可以安全地刪除indexA嗎?
- 如何衡量每個索引的大小?我所得到的是所有指標的總和。
如果你可以爲任何大型表運行一些'show create table'併發布輸出將會很有幫助。 – 2011-04-19 08:08:15