当外键存在时 MySQL 5.5 外键约束失败

Question

刚刚在 mac os x 10.6 上安装了 MySQL 5.5，我在许多表上遇到了一个奇怪的问题。下面是一个例子。插入一行在不应该的情况下因外键约束而失败。它引用的外键确实存在。有什么想法吗？

mysql> show create table Language;
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Language | CREATE TABLE `Language` (
  `Id` int(11) NOT NULL AUTO_INCREMENT,
  `Code` varchar(2) NOT NULL,
  `Name` varchar(63) CHARACTER SET utf8 DEFAULT NULL,
  `Variant` varchar(63) CHARACTER SET utf8 DEFAULT NULL,
  `Country_Id` int(11) DEFAULT NULL,
  PRIMARY KEY (`Id`),
  UNIQUE KEY `Code` (`Code`,`Country_Id`,`Variant`),
  KEY `FKA3ACF7789C1796EB` (`Country_Id`),
  CONSTRAINT `FKA3ACF7789C1796EB` FOREIGN KEY (`Country_Id`) REFERENCES `Country` (`Id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1 |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> show create table Language_Phrases;
+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table            | Create Table                                                                                                                                                                                                                                                                                                                                                    |
+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Language_Phrases | CREATE TABLE `Language_Phrases` (
  `Language_Id` int(11) NOT NULL,
  `Phrase` varchar(255) DEFAULT NULL,
  `Label` varchar(255) NOT NULL,
  PRIMARY KEY (`Language_Id`,`Label`),
  KEY `FK8B4876F3AEC1DBE9` (`Language_Id`),
  CONSTRAINT `FK8B4876F3AEC1DBE9` FOREIGN KEY (`Language_Id`) REFERENCES `Language` (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select * from Language;
+----+------+----------+---------+------------+
| Id | Code | Name     | Variant | Country_Id |
+----+------+----------+---------+------------+
|  1 | en   | English  |         |        235 |
|  2 | ro   | Romanian |         |        181 |
+----+------+----------+---------+------------+
2 rows in set (0.00 sec)

mysql> select * from Language_Phrases;
Empty set (0.00 sec)

mysql> INSERT INTO Language_Phrases (Language_Id, Label, Phrase) VALUES (1, 'exampleLabel', 'Some phrase');
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`dev`.`language_phrases`, CONSTRAINT `FK8B4876F3AEC1DBE9` FOREIGN KEY (`Language_Id`) REFERENCES `Language` (`Id`))
mysql> 

更新:删除并重新创建数据库几次后，我在上面的插入失败后做了一个show engine innodb status并得到了这个令人惊讶的结果。未找到父语言表!这看起来很奇怪……有什么想法吗？

------------------------
LATEST FOREIGN KEY ERROR
------------------------
110406  9:55:49 Transaction:
TRANSACTION CA3B, ACTIVE 0 sec, OS thread id 4494462976 inserting
mysql tables in use 1, locked 1
1 lock struct(s), heap size 376, 0 row lock(s)
MySQL thread id 25, query id 50720 localhost root update
INSERT INTO Language_Phrases (Language_Id, Label, Phrase) VALUES (1, 'exampleLabel', 'Some phrase')
Foreign key constraint fails for table `dev`.`language_phrases`:
,
  CONSTRAINT `FK8B4876F3AEC1DBE9` FOREIGN KEY (`Language_Id`) REFERENCES `Language` (`Id`)
Trying to add to index `PRIMARY` tuple:
DATA TUPLE: 5 fields;
 0: len 4; hex 80000001; asc     ;;
 1: len 17; hex 747970654d69736d617463682e79656172; asc exampleLabel;;
 2: len 6; hex 00000000ca3b; asc      ;;;
 3: len 7; hex 00000000000000; asc        ;;
 4: len 21; hex 59656172206d7573742062652061206e756d626572; asc Some phrase;;

But the parent table `dev`.`Language`
or its .ibd file does not currently exist!

更新 2:事实证明这只是 MySQL 中的一个大错误。显然，最新版本的 MySQL 在 mac os X 10.6 下不能完全工作(也许早期版本也是如此？)。降级到 5.5.8 似乎可行。非常令人惊讶。

Answer 1

这似乎是自 Mac OS X 上的 MySQL 5.5.9 以来引入的错误: http://bugs.mysql.com/bug.php?id=60309

它在 5.5.13(5 月 31 日发布)中被标记为已修复，并在发行说明中提到: http://dev.mysql.com/doc/refman/5.5/en/news-5-5-13.html

或者，我在 5.5.10 上验证并在下面复制的错误报告中列出了一个解决方法:

[20 Mar 11:29] Harald NeissI also received a new MBP and reinstalled MySQL (mysql-5.5.10-osx10.6-x86_64). Finally Icame across the same problem as described above. So here is the query result and what Idid to solve it.mysql> show variables like 'lower%';+------------------------+-------+| Variable_name          | Value |+------------------------+-------+| lower_case_file_system | ON    || lower_case_table_names | 2     |+------------------------+-------+2 rows in set (0.00 sec)Dropped database, created the file /etc/my.cnf with the following content:[mysqld]lower_case_table_names=1Restarted the MySQL daemon and repeated the query:mysql> show variables like 'lower%';+------------------------+-------+| Variable_name          | Value |+------------------------+-------+| lower_case_file_system | ON    || lower_case_table_names | 1     |+------------------------+-------+2 rows in set (0.00 sec)I recreated the tables and everything works fine.