mysql索引优化
2016-04-25 19:47:28 来源: 阅读:
原创文章，转载请注明。时间：2016-03-31
问题：cpu负载过高，达到36。
现象：通过mysqladmin -uroot -p processlist 查看到大量如下信息：
Sending data select * from `rep_corp_vehicle_online_count` where corp_id = 48 and vehicle_id = 10017543
根据以上的可能是表rep_corp_vehicle_online_count的问题 做出如下信息收集：
查看表结构：
mysql> desc rep_corp_vehicle_online_count;+-------------+-------------+------+-----+---------+----------------+| Field | Type | Null | Key | Default | Extra |+-------------+-------------+------+-----+---------+----------------+| id | int(11) | NO | PRI | NULL | auto_increment || corp_id | int(11) | NO | | NULL | || vehicle_id | int(11) | NO | | NULL | || online_day | varchar(20) | NO | | NULL | || loc_total | int(11) | NO | | NULL | || create_time | datetime | NO | | NULL | || update_time | datetime | NO | | NULL | |+-------------+-------------+------+-----+---------+----------------+7 rows in set (0.00 sec)
查看索引，只有主键索引：
mysql> show index from rep_corp_vehicle_online_count;+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+| rep_corp_vehicle_online_count | 0 | PRIMARY | 1 | id | A | 1247259 | NULL | NULL | | BTREE | | |+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+1 row in set (0.00 sec)
代码效率执行情况：
mysql>explain select * from rep_corp_vehicle_online_count where corp_id = 79 and vehicle_id = 10016911 and online_day = '2016-03-29'G*************************** 1. row *************************** id: 1 select_type: SIMPLE table: rep_corp_vehicle_online_count type: ALLpossible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 1248495 Extra: Using where1 row in set (0.00 sec)
表数据分析情况，重复数据很多：
mysql> select count(distinct corp_id) from rep_corp_vehicle_online_count;+-------------------------+| count(distinct corp_id) |+-------------------------+| 18 |+-------------------------+1 row in set (0.63 sec)mysql> select count(corp_id) from rep_corp_vehicle_online_count; +----------------+| count(corp_id) |+----------------+| 1239573 |+----------------+1 row in set (0.00 sec)mysql> select count(distinct vehicle_id) from rep_corp_vehicle_online_count; +----------------------------+| count(distinct vehicle_id) |+----------------------------+| 2580 |+----------------------------+1 row in set (1.03 sec)mysql>explain select count(vehicle_id) from rep_corp_vehicle_online_count; +-------------------+| count(vehicle_id) |+-------------------+| 1239911 |+-------------------+1 row in set (0.00 sec)
最后处理，创建索引：
mysql> create index r_c_v on rep_corp_vehicle_online_count(corp_id,vehicle_id); Query OK, 1487993 rows affected (6.09 sec)Records: 1487993 Duplicates: 0 Warnings: 0
mysql> show index from rep_corp_vehicle_online_count;+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+| rep_corp_vehicle_online_count | 0 | PRIMARY | 1 | id | A | 1490176 | NULL | NULL | | BTREE | | || rep_corp_vehicle_online_count | 1 | r_c_v | 1 | corp_id | A | 18 | NULL | NULL | | BTREE | | || rep_corp_vehicle_online_count | 1 | r_c_v | 2 | vehicle_id | A | 2596 | NULL | NULL | | BTREE | | |+-------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+3 rows in set (0.00 sec)
添加索引过后负载降低到了1.73：
Tags：mysql索引优化
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