MySQL 不使用索引进行 BETWEEN 查询。我究竟做错了什么？

Question

我尝试了此查询的不同变体，但我就是无法让它使用时间戳索引。我做错了什么？

任何帮助将不胜感激:)

---

MariaDB [alienvault]> explain extended SELECT * FROM alienvault_siem.acid_event WHERE (timestamp BETWEEN '2012-10-09 11:20:17' AND '2012-10-10 03:20:17');
+------+-------------+------------+------+---------------+------+---------+------+---------+----------+-------------+
| id   | select_type | table      | type | possible_keys | key  | key_len | ref  | rows    | filtered | Extra       |
+------+-------------+------------+------+---------------+------+---------+------+---------+----------+-------------+
|    1 | SIMPLE      | acid_event | ALL  | timestamp     | NULL | NULL    | NULL | 4481579 |    50.00 | Using where |
+------+-------------+------------+------+---------------+------+---------+------+---------+----------+-------------+
1 row in set, 1 warning (0.01 sec)

表结构:

CREATE TABLE IF NOT EXISTS `acid_event` (
  (...)
  `timestamp` datetime NOT NULL,
  (...)
  PRIMARY KEY (`id`),
  (...)
  KEY `timestamp` (`timestamp`),
  (...)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

软件:Percona 服务器

软件版本:5.5.27-28.1 - Percona Server (GPL)，28.1 版

Answer 1

可能由以下原因引起: - 索引的选择性不够，mysql 认为全扫描会更快 - mysql 有错误的索引统计信息

您可以检查“SHOW INDEX FROM alienvault_siem.acid_event;”的输出您还可以尝试强制使用索引(但如果全扫描速度更快，则可能会很糟糕):

SELECT * FROM alienvault_siem.acid_event FORCE INDEX (`timestamp`) WHERE (timestamp BETWEEN '2012-10-09 11:20:17' AND '2012-10-10 03:20:17');