slowlog里查到一条sql执行了10秒钟以上

# Time: 2017-03-02T18:41:50.201376+08:00

# User@Host: oms_readonly[oms_readonly] @ [10.xx.xx.xx] Id: 54124620

# Query_time: 11.005894 Lock_time: 0.000223 Rows_sent: 20 Rows_examined: 1838114

SET timestamp=1488451310;

select * from customers where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;

查看执行计划

mysql> explain select * from customers where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;

+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+

| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |

+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+

| 1 | SIMPLE | customers | NULL | index | type,into_time,isarea,status,idx_isarea_renew_owner,type_status | score | 2 | NULL | 603 | 0.21 | Using where |

+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+

1 row in set, 1 warning (0.00 sec)

看下列的选择性，很明显isarea列的选择性更好

mysql> select count(*) from customers where `type` = 1;

+----------+

| count(*) |

+----------+

| 2373175 |

+----------+

1 row in set (1.53 sec)

mysql> select count(*) from customers where `status` < 7;

    -> ;

+----------+

| count(*) |

+----------+

| 2494232 |

+----------+

1 row in set (3.16 sec)

mysql> select count(*) from customers where `isarea` = 6;

+----------+

| count(*) |

+----------+

| 135347 |

+----------+

1 row in set (0.15 sec)

mysql> select count(*) from customers where `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59';

+----------+

| count(*) |

+----------+

| 106158 |

+----------+

1 row in set (0.12 sec)

isarea有索引，强制用这个列的索引

mysql> explain select * from customers use index(isarea) where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;

+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+

| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |

+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+

| 1 | SIMPLE | customers | NULL | ref | isarea | isarea | 5 | const | 249438 | 1.85 | Using index condition; Using where; Using filesort |

+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+

1 row in set, 1 warning (0.00 sec)

优化前10几秒出结果，优化后0.5秒出结果。