今天接到一个朋友电话说是觉的数据库被别人更改了,出现数据不对的问题 。经过很久的排查是数据类型溢出了(发生问题的版本是MySQL 5.1)。后来通过给朋友那边把MySQL 5.1升级到MySQL 5.5去解决这个问题。 这也让我有兴趣去了解一下MySQL不同版本数据类型溢出的处理机制。
先看一下MySQL支持的整型数及大小,存储空间:
Type | Storage | Minimum Value | Maximum Value | 存储大小 |
---|---|---|---|---|
(Bytes) | (Signed/Unsigned) | (Signed/Unsigned) | byte | |
TINYINT | 1 | -128 | 127 | 1 byte |
0 | 255 | |||
SMALLINT | 2 | -32768 | 32767 | 2 bytes |
0 | 65535 | |||
MEDIUMINT | 3 | -8388608 | 8388607 | 3 bytes |
0 | 16777215 | |||
INT | 4 | -2147483648 | 2147483647 | 4 bytes |
0 | 4294967295 | |||
BIGINT | 8 | -9223372036854775808 | 9223372036854775807 | 8 bytes |
0 | 18446744073709551615 |
另外请记着mysql的数据处理会转成bigint处理,所以这里就用bigint几个测试:
<span style="font-weight: bold; color: #993333;">SELECT</span> <span style="font-weight: bold; color: #993333;">CAST</span><span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0</span> <span style="font-weight: bold; color: #993333;">AS</span> <span style="font-weight: bold; color: #993333;">UNSIGNED</span><span style="color: #66cc66;">)</span> <span style="color: #66cc66;">-</span> <span style="color: #cc66cc;">1</span>; <span style="font-weight: bold; color: #993333;">SELECT</span> <span style="color: #cc66cc;">9223372036854775807</span> <span style="color: #66cc66;">+</span> <span style="color: #cc66cc;">1</span>; |
MySQL 5.1 下:
mysql<span style="color: #66cc66;">></span> <span style="font-weight: bold; color: #993333;">SELECT</span> <span style="font-weight: bold; color: #993333;">CAST</span><span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0</span> <span style="font-weight: bold; color: #993333;">AS</span> <span style="font-weight: bold; color: #993333;">UNSIGNED</span><span style="color: #66cc66;">)</span> <span style="color: #66cc66;">-</span> <span style="color: #cc66cc;">1</span>; <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #66cc66;">|</span> <span style="font-weight: bold; color: #993333;">CAST</span><span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0</span> <span style="font-weight: bold; color: #993333;">AS</span> <span style="font-weight: bold; color: #993333;">UNSIGNED</span><span style="color: #66cc66;">)</span> <span style="color: #66cc66;">-</span> <span style="color: #cc66cc;">1</span> <span style="color: #66cc66;">|</span> <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #66cc66;">|</span> <span style="color: #cc66cc;">18446744073709551615</span> <span style="color: #66cc66;">|</span> <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #cc66cc;">1</span> <span style="font-weight: bold; color: #993333;">ROW</span> <span style="font-weight: bold; color: #993333;">IN</span> <span style="font-weight: bold; color: #993333;">SET</span> <span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0.01</span> sec<span style="color: #66cc66;">)</span> mysql<span style="color: #66cc66;">></span> <span style="font-weight: bold; color: #993333;">SELECT</span> <span style="color: #cc66cc;">9223372036854775807</span> <span style="color: #66cc66;">+</span> <span style="color: #cc66cc;">1</span>; <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #66cc66;">|</span> <span style="color: #cc66cc;">9223372036854775807</span> <span style="color: #66cc66;">+</span> <span style="color: #cc66cc;">1</span> <span style="color: #66cc66;">|</span> <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #66cc66;">|</span> <span style="color: #66cc66;">-</span><span style="color: #cc66cc;">9223372036854775808</span> <span style="color: #66cc66;">|</span> <span style="color: #66cc66;">+</span><span style="font-style: italic; color: #808080;">-------------------------+</span> <span style="color: #cc66cc;">1</span> <span style="font-weight: bold; color: #993333;">ROW</span> <span style="font-weight: bold; color: #993333;">IN</span> <span style="font-weight: bold; color: #993333;">SET</span> <span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0.01</span> sec<span style="color: #66cc66;">)</span> |
MySQL 5.5, 5.6, 5.7下:
mysql<span style="color: #66cc66;">></span> <span style="font-weight: bold; color: #993333;">SELECT</span> <span style="font-weight: bold; color: #993333;">CAST</span><span style="color: #66cc66;">(</span><span style="color: #cc66cc;">0</span> <span style="font-weight: bold; color: #993333;">AS</span> <span style="font-weight: bold; color: #993333;">UNSIGNED</span><span style="color: #66cc66;">)</span> <span style="color: #66cc66;">-</span> <span style="color: #cc66cc;">1</span>; ERROR <span style="color: #cc66cc;">1690</span> <span style="color: #66cc66;">(</span><span style="color: #cc66cc;">22003</span><span style="color: #66cc66;">)</span>: <span style="font-weight: bold; color: #993333;">BIGINT</span> <span style="font-weight: bold; color: #993333;">UNSIGNED</span> <span style="font-weight: bold; color: #993333;">VALUE</span> <span style="font-weight: bold; color: #993333;">IS</span> <span style="font-weight: bold; color: #993333;">OUT</span> <span style="font-weight: bold; color: #993333;">OF</span> range <span style="font-weight: bold; color: #993333;">IN</span> <span style="color: #ff0000;">'(cast(0 as unsigned) - 1)'</span> mysql<span style="color: #66cc66;">></span> mysql<span style="color: #66cc66;">></span> mysql<span style="color: #66cc66;">></span> mysql<span style="color: #66cc66;">></span> <span style="font-weight: bold; color: #993333;">SELECT</span> <span style="color: #cc66cc;">9223372036854775807</span> <span style="color: #66cc66;">+</span> <span style="color: #cc66cc;">1</span>; ERROR <span style="color: #cc66cc;">1690</span> <span style="color: #66cc66;">(</span><span style="color: #cc66cc;">22003</span><span style="color: #66cc66;">)</span>: <span style="font-weight: bold; color: #993333;">BIGINT</span> <span style="font-weight: bold; color: #993333;">VALUE</span> <span style="font-weight: bold; color: #993333;">IS</span> <span style="font-weight: bold; color: #993333;">OUT</span> <span style="font-weight: bold; color: #993333;">OF</span> range <span style="font-weight: bold; color: #993333;">IN</span> <span style="color: #ff0000;">'(9223372036854775807 + 1)'</span> |
所在处理这类数据是一定要小心溢出(如早期有做弊冲Q币就是利用这个方法处理)
这个问题有可能会出现积分消息,积分相加, 或是一些钱相关的业务中出现, 主库5.1 ,从库MySQL 5.5情况也会出现不同步的问题。
建议:这类业务系统尽可能的升级到MySQL 5.5后版本
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