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更新text字段时出现Row size too large报错应付措施

WBOY
WBOYOriginal
2016-06-07 17:55:321102browse

个人建议:表的text字段很多建议建表时加上 row_format = dynamic当然,回过头来MySQL的报错也是有误导性的,感兴趣的你可以参考下本文

起因
团购开发报告说更新时出错。

更新SQL如下
代码如下:
UPDATE table_name d SET d.column_name='aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
WHERE d.ID=100976;

报错信息如下
Error Code : 1118
Row size too large. The maximum row size for the used table type, not counting BLOBs, is 8126. You have to change some columns to TEXT or BLOBs
疑惑
更新字段只涉及 column_name字段,且该字段是TEXT类型。

个人之前理解是
TEXT的内容在 Dynamic的table format下是存在off-page中的,不会占用row size的计算。
Barracuda 对应row_format ( dynamic, compress) ,其中dynamic下text的所有内容都是off-page存放的 (点击查看)
Antelope 对应row_format (compact, redundant),其中compact下的text是存786B在row中,超过部分存在off-page
而服务器配置是 innodb_file_format = Barracuda
照理说所有table用的都是 dynamic 结构。
但是! 原因如下,摘自文档:
To preserve compatibility with those prior versions, tables created with the InnoDB Plugin use the prefix format, unless one of ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED is specified (or implied) on the CREATE TABLE command.
也就是说,建表时不显示指定 row_format = dynamic ,即使 innodb_file_format = Barracuda 表的row-format还是 compact

所以总结为一句话就是:如果某个表的text字段很多建议建表时加上 row_format = dynamic
当然,回过头来MySQL的报错也是有误导性的,bug库中也对confirm了这个bug(点击查看),并在5.1.61中优化了报错提示。
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