Eiriks Eiriks - 2 months ago 8
MySQL Question

Why does mysql connector break ("Lost connection to MySQL server during query" error)

When I run large queries (queries returning many rows), I get the

Lost connection to MySQL server during query
error, and I cannot see what I do wrong. I use the "new" mysql driver from mysql.com (not the "old" MySQLdb), and the mysql version that is bundled with MAMP. Python 2.7. Table is not corrupted,
analyze table nrk2013b_tbl;
returns status ok. Here's an example that breaks:

#!/usr/bin/python2.7
# coding: utf-8

import sys
import mysql.connector # version 2.0.1

connection = mysql.connector.connect(
unix_socket="/Applications/MAMP/tmp/mysql/mysql.sock",
user="dbUsernam",
passwd="dbUserPassword",
db="nrk",
charset = "utf8",
use_unicode = True)
cur = connection.cursor()
cur.execute("USE nrk;")


sql = """SELECT id FROM nrk2013b_tbl WHERE main_news_category = 'Sport'"""
cur.execute(sql)
rows = cur.fetchall()

print rows

sys.exit(0)


This results in the error I get most of the time:

Traceback (most recent call last):
File "train_trainer_test.py", line 20, in <module>
remaining_rows = cur.fetchall()
File "/Library/Python/2.7/site-packages/mysql/connector/cursor.py", line 823, in fetchall
(rows, eof) = self._connection.get_rows()
File "/Library/Python/2.7/site-packages/mysql/connector/connection.py", line 669, in get_rows
rows = self._protocol.read_text_result(self._socket, count)
File "/Library/Python/2.7/site-packages/mysql/connector/protocol.py", line 309, in read_text_result
packet = sock.recv()
File "/Library/Python/2.7/site-packages/mysql/connector/network.py", line 226, in recv_plain
raise errors.InterfaceError(errno=2013)
mysql.connector.errors.InterfaceError: 2013: Lost connection to MySQL server during query


Line 20 is the
rows = cur.fetchall()


If I limit the query to result fewer result
SELECT id FROM nrk2013b_tbl WHERE main_news_category = 'Sport' LIMIT 10
all is well. But I do want to work with larger result sets. For some ad-hoc problem solving I have moved the limit and broken down the data I wanted into smaller batches, but this keeps popping up as a problem.

In order to take connect-timeout, and max_allowed_packet, etc into account, I have this my.cnf-file:
File: /Applications/MAMP/conf/my.cnf


[mysqld]
max_allowed_packet = 64M
wait_timeout = 28800
interactive_timeout = 28800
connect-timeout=31536000


This does not seem to make any difference (I'm not even sure if mysql recognises these settings). When I run queries from the terminal or from Sequel Pro, it works fine. It is only through the python mysql.connector I get these errors.

Any ideas?

PS: I've temporarily given this up, and changed to PyMySQL instead of of the Oracle mysql.connector. By changing to this, the problems seems to disappear (and I conclude for myself that the problem is in the oracle mysql connector).

import pymysql
conn = pymysql.connect(
unix_socket="/Applications/MAMP/tmp/mysql/mysql.sock",
user="dbUsernam",
passwd="dbUserPassword",
db="nrk",
charset = "utf8",
use_unicode = True)
conn.autocommit(True) # this I
cur = conn.cursor()

Answer

I also had to switch to PyMySQL. I am running pip 1.5.6, Python 2.7.8, and tried mysql-connector 2.0.1

I was able to run the query from within Sequel Pro with no problems, but my Python query would fail with the error described in the question after returning just a subset of results.

Switched to PyMySQL and things work as expected.

https://github.com/PyMySQL/PyMySQL

In the virtualenv:

pip install pymysql

In the code:

import pymysql

connection = pymysql.connect(user='x', passwd='x',
                                 host='x',
                                 database='x')

cursor = connection.cursor()

query = ("MYQUERY")

cursor.execute(query)

for item in cursor:
    print item

Definitely a bug in mysql-connector-python.