解决MySQL创建主键报错1878：No space left on device-优快云博客

在尝试为大数据量表OFFER添加主键时遇到1878错误，原因是操作系统返回了'No space left on device'，即磁盘空间不足。该问题与MySQL的tmpdir变量相关，临时文件写入失败。解决方案包括清理/tmp目录的临时文件或更改tmpdir值以指向有足够空间的位置。

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大数据量创建主键报错：

mysql> alter table OFFER add constraint pk_offer primary key (offer_id);
ERROR 1878 (HY000): Temporary file write failure.

查看error.log:

2014-09-01 11:44:01 7fca70b8d700 InnoDB: Error: Write to file (merge) failed at offset 2105540608.
InnoDB: 1048576 bytes should have been written, only 913408 were written.
InnoDB: Operating system error number 28.
InnoDB: Check that your OS and file system support files of this size.
InnoDB: Check also that the disk is not full or a disk quota exceeded.
InnoDB: Error number 28 means 'No space left on device'.
InnoDB: Some operating system error numbers are described at
InnoDB: http://dev.mysql.com/doc/refman/5.6/en/operating-system-error-codes.html

没有多余的空间，这个和tmpdir参数有关系，在创建index、主键的时候需要创建一个临时文件做排序，默认情况下是
mysql> show variables like 'tmp%';
+----------------+----------+
| Variable_name | Value |
+----------------+----------+
| tmpdir | /tmp |
+----------------+----------+

空间不足，将 /tmp 下的临时文件清空或者修改tmpdir的值，指向一个大的空间就可以了。

错误相关：http://dev.mysql.com/doc/refman/5.6/en/operating-system-error-codes.html