Convert from unsigned long long to PyLong

[Tian JiaLin]

HI There,

I'm using MySQLdb as the MySQL client. Recently I got a weird problem of this library. After looking into it, I suspect the problem may related to the conversion from unsigned long to PyLongObject.

Here is the detail, If you are familiar with MySQLdb, the following snippet is a way to query the data from MySQL:


connection = MySQLdb.connect(...)

connection.autocommit(True)
try:
cursor = connection.cursor()
if not cursor.execute(sql, values) > 0:
return None
row = cursor.fetchone()
finally:
connection.close()
return row[0]


Sometimes the return value of execute method would be 18446744073709552000 even there is no matched data available. I checked the source code of the library, the underlying implementation is https://github.com/farcepest/MySQLdb1/blob/master/_mysql.c#L835,

static PyObject *
_mysql_ConnectionObject_affected_rows(
_mysql_ConnectionObject *self,
PyObject *args)
{
if (!PyArg_ParseTuple(args, "")) return NULL;
check_connection(self);
return PyLong_FromUnsignedLongLong(mysql_affected_rows(&(self->connection)));
}

And here is the official doc for mysql_affected_rows http://dev.mysql.com/doc/refman/5.7/en/mysql-affected-rows.html.

Let me give a superficial understanding, please correct me if I were wrong.

In a 64-bit system, the mysql_affected_rows is supposed to return a number of unsigned long, which means the range should be 0 ~ 2^64 (18446744073709551616), How could it be possible the function PyLong_FromUnsignedLongLong return a converted value larger than 2^64, that's what I don't understand.

Does anyone have some ideas of it?


The versions of the components I used:

Python: 2.7.6
MySQL 5.7.11
MySQLdb 1.2.5


Thanks

[MRAB]

The function returns an unsigned value, but it will return -1 (i.e. ~0)
if there's an error, so check for an error with ~result == 0.

[INADA Naoki]

Thank you for reporting this issue.

I'll fix it in next release of mysqlclient

(MySQL-python has not been maintained for these years. Please use mysqlclient.
It supports Python 3.)

> --
> https://mail.python.org/mailman/listinfo/python-list



--
INADA Naoki <songof...@gmail.com>