Question

我正在使用分区创建表格，如下所示：

CREATE TABLE `alert` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `eventId` int(10) unsigned NOT NULL,
  `occurred` datetime NOT NULL,
  KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin
/*!50100 PARTITION BY RANGE (TO_DAYS(occurred))
(PARTITION 28_06 VALUES LESS THAN (735413) ENGINE = InnoDB,
 PARTITION 29_06 VALUES LESS THAN (735414) ENGINE = InnoDB,
 PARTITION 30_06 VALUES LESS THAN (735415) ENGINE = InnoDB,
 PARTITION 01_07 VALUES LESS THAN (735416) ENGINE = InnoDB,
 PARTITION 02_07 VALUES LESS THAN (735417) ENGINE = InnoDB,
 PARTITION 03_07 VALUES LESS THAN (735418) ENGINE = InnoDB,
 PARTITION 04_07 VALUES LESS THAN (735419) ENGINE = InnoDB,
 PARTITION 05_07 VALUES LESS THAN (735420) ENGINE = InnoDB,
 PARTITION 06_07 VALUES LESS THAN (735421) ENGINE = InnoDB,
 PARTITION 07_07 VALUES LESS THAN (735422) ENGINE = InnoDB) */

一切似乎都正常，但是当我执行以下查询时：

EXPLAIN PARTITIONS SELECT * FROM alert WHERE occurred >= '2013-06-30' AND occurred <= '2013-07-01';

我得到以下输出：

+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | partitions        | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+
|  1 | SIMPLE      | alert | 28_06,30_06,01_07 | ALL  | NULL          | NULL | NULL    | NULL |    3 | Using where |
+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+

为什么分区28_06出现在这些结果中？当我非常清楚地选择开始2013-06-30。

有什么想法吗？

奇怪的是，以下查询似乎没问题：

EXPLAIN PARTITIONS SELECT * FROM alert WHERE occurred >= '2013-07-02' AND occurred <= '2013-07-04';

输出：

+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | partitions        | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+
|  1 | SIMPLE      | alert | 02_07,03_07,04_07 | ALL  | NULL          | NULL | NULL    | NULL |    3 | Using where |
+----+-------------+-------+-------------------+------+---------------+------+---------+------+------+-------------+

Answer 1

看起来这是一个回归错误。我在Mac OS X 10.8上使用的是5.6.11版本。

http://bugs.mysql.com/bug.php?id=49754

解决方案是在开头创建一个从未使用过的分区。即：

PARTITION unused VALUES LESS THAN (0)

为什么这个MySql查询（在分区表上）总是命中第一个分区？

1 个答案: