They tell me that my hosting this edition of Log Buffer; the weekly intersection of all things DBA and blog; has nothing to do with my birthday being on Sunday, but if it’s all the same I’d like to think of it as a pre-emptive strike against my birth…

Yes I can be wrong regarding what really happens internally. I just know if you just echo it out it will be signed on 32bit platforms and always positive on 64bit platforms. It well may be wrapping around thing.

I know about sprintf thing but in this case it was existing application with existing data so it was not changed.

But you’re right if I would be dealing with same problem today I would use sprintf for compatibility reasons and have field unsigned.

As far as I checked, the problem is not the conversion to string, but the fact 64bit php returns a 64 bit signed integer which wont wrap at the same position as a 32bit signed integer.
I’ve solved my problems by using sprintf(‘%u’,crcvalue) when crcvalue is negative and then store all crc32 values as unsigned integers in mysql.

You’re right this is the problem and this is why MySQL 5.0 gets strict mode.

If you however look at general pictures in many cases people select simple thing compared to reliable thing. For example so widely popular PHP does not require variables to be declared neither has exact types which cause numerous security and reliability problems.

Same applies to MySQL most of MySQL user base loading some dirty data to MySQL would rather like it to be truncated int the case when unexpected data is found rather than ball out and require investigations on how to convert it right.

For other group reliability is more important, and they usually only started using MySQL in the recent years – this is where we get Strict mode and similar changes from.

This is not the point. Things should be working with CRC32 as well. For this task MD5 or SHA1 are not good fit as they are too long and what I need it short keys even if it means a bit higher collision rate.

I might be mistaken and it could be it is just int which wraps around in 32bit but not at 64bit, but the fact is if you echo/convert it to string you’ll get different value in 32bit and 64bit versions.

Thanks for mentioning, am now recalculating all crc32 values in my mixed environment setup