Bug _mysql.c - binary flag?

Hi,

Thanks for your effort providing us this driver.

However, I think there is a bug in _mysql.c. In the function "_mysql_field_to_python" there is a switch statement. In this statement the binary flag is always overwritten by the default block.
As a consequence I'm getting trouble processing binary data because the binary data is treated as text leading into conversion trouble.
I wanted to let you know about the problem, because you might want to check.

Thanks and regards!

It is not a bug, as comment describes.
What field type do you using?

Are you really sure about that?
I'm not an expert in C, but since there is no break after setting binary to 1, binary is always overwritten to 0 due to the default. The comment does not explain any implicit meaning behind that.

You're right. But I don't have failing test case. What type do you use?

I think it depends on the configuration. I use my own converter callbacks with the option "use_unicode=0"

conv = {
	252: ((128 ,_BINARYCONV  ),(None,_STRINGCONV)),
	250: ((128 ,_BINARYCONV  ),(None,_STRINGCONV)),
	251: ((128 ,_BINARYCONV  ),(None,_STRINGCONV)),
	253: ((128 ,_BINARYCONV  ),(None,_STRINGCONV)),
	254: ((128 ,_BINARYCONV  ),(None,_STRINGCONV)),
	....
}
MySQLdb.connect(
	...
	conv        = conv,
	use_unicode = 0,
	...
)

Hope this information is helpful...

Uh, that's API I hate.... conv waste my hundreds hours. It's broken design.
Why you need it?

Sorry to hear that. We tend to manage any encoding operations on our own. The conv seems to be a reasonable tool. Of course, we can workaround that with use_unicode, but that doesn't solve the bug.

Of course, we can workaround that with use_unicode, but that doesn't solve the bug.

If you didn't override these types, this switch statement is not used.
That's why only you are affected by this bug.

https://github.com/PyMySQL/mysqlclient-python/blob/1a67ae2cc2da1a2bf511cf70b20dcd5fca5ba7fe/MySQLdb/_mysql.c#L1110-L1123

I was already wondering why no others were affected. Thanks for your attention.

I just hit this same bug today, and have pull request.

So if this is broken it becomes really hard to deal with databases that have bad charsets or what have you. The example I have is we have some really old db's where the charset is utf8, but some bad C++ code was committing truncated data to the table, and thus was not possible to decode it, The team fixed the C++, but it might be still possible that some of this data still exists, so they have a converter that opens a task for a human to resolve, but returns the value by doing a decode(utf8, 'ignore')

Even though this bug is fixed, I won't guarantee the callback is supported in such ways.
Use only use_unicode=False. Don't override callbacks for strs.

Add missing break (PyMySQL#346)

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Bug _mysql.c - binary flag? #343

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Bug _mysql.c - binary flag? #343

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methane commented on Mar 14, 2019

mire1221 commented on Mar 14, 2019

methane commented on Mar 14, 2019

mire1221 commented on Mar 15, 2019

methane commented on Mar 15, 2019

mire1221 commented on Mar 15, 2019

methane commented on Mar 15, 2019

mire1221 commented on Mar 15, 2019

fried commented on Mar 19, 2019

fried commented on Mar 19, 2019

methane commented on Mar 19, 2019

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