Question

What’s going on here? BTW, MySQL Server version: 5.0.45-log Source distribution.

mysql> select count(*) 
       from notes 
      where date(updated_at) > date('2010-03-25');
+----------+
| count(*) |
+----------+
|        0 | 
+----------+
1 row in set (0.59 sec)

mysql> select count(*) 
         from notes 
        where message like'%***%' 
          and date(updated_at) > date('2010-03-25');
+----------+
| count(*) |
+----------+
|       26 | 
+----------+
1 row in set (1.30 sec)

mysql> explain select count(*) 
      from notes 
      where date(updated_at) > date('2010-03-25');
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows   | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
|  1 | SIMPLE      | notes | ALL  | NULL          | NULL | NULL    | NULL | 588106 | Using where | 
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
1 row in set (0.07 sec)

mysql> explain select updated_at 
         from notes 
        where message like'%***%' 
          and date(updated_at) > date('2010-03-25');
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows   | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
|  1 | SIMPLE      | notes | ALL  | NULL          | NULL | NULL    | NULL | 588106 | Using where | 
+----+-------------+-------+------+---------------+------+---------+------+--------+-------------+
1 row in set (0.09 sec)

mysql> 

Here’s the table schema.

CREATE TABLE `notes` (
 `id` int(11) NOT NULL auto_increment,
 `status` varchar(255) default NULL,
 `message` text,
 `noteable_id` int(11) default NULL,
 `noteable_type` varchar(255) default NULL,
 `deleted_at` datetime default NULL,
 `creator_id` int(11) default NULL,
 `updater_id` int(11) default NULL,
 `deleter_id` int(11) default NULL,
 `created_at` datetime default NULL,
 `updated_at` datetime default NULL,
 `public` tinyint(1) default '0',
 `forced` tinyint(1) default '0',
 `agent_created_at` datetime default NULL,
 PRIMARY KEY  (`id`),
 KEY `noteable_id` (`noteable_id`),
 KEY `deleted_at` (`deleted_at`),
 KEY `noteable_type` (`noteable_type`(10)),
 KEY `creator_id` (`creator_id`),
 KEY `status` (`status`),
 KEY `created_at` (`created_at`)
) ENGINE=InnoDB AUTO_INCREMENT=613168 DEFAULT CHARSET=latin1 

Answer 1

It turns out, this particular instance was not caused by database corruption, but a bug in the Date function for MySQL version 5.0.45 (+?).

http://bugs.mysql.com/bug.php?id=32159

We don’t see a need to react to this situation immediately, but we will be migrating to a higher version of MySQL (either 5.0.77+ or 5.1)