Data truncated for column 'url' at row 1 - Error with programming with Python Django

Question

The error message I got was

Traceback (most recent call last):
  File "./test.py", line 416, in <module>
    startup()
  File "./test.py", line 275, in startup
    writer.save(r,data) 
  File "/home/user/project/test/output.py", line 91, in save
    self.save_doc(r, data, pid)
  File "/home/user/project/test/output.py", line 130, in save_doc
    cursor.execute(dbquery)
  File "/usr/local/lib/python2.6/site-packages/django/db/backends/util.py", line 34, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.6/site-packages/django/db/backends/mysql/base.py", line 86, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/lib/python2.6/site-packages/MySQL_python-1.2.3c1-py2.6-linux-x86_64.egg/MySQLdb/cursors.py", line 175, in execute
  File "/usr/local/lib/python2.6/site-packages/MySQL_python-1.2.3c1-py2.6-linux-x86_64.egg/MySQLdb/cursors.py", line 89, in _warning_check
_mysql_exceptions.Warning: Data truncated for column 'url' at row 1

The first thing I was checking is if the URL string is longer than the field length, but it is actually much shorter. Database Design

+----------+-------------------------------------------------------------------+
| Database | Create Database                                                   |
+----------+-------------------------------------------------------------------+
| myurlcol | CREATE DATABASE `myurlcol` /*!40100 DEFAULT CHARACTER SET utf8 */ | 
+----------+-------------------------------------------------------------------+

Table Design

  CREATE TABLE `document` (
  `id` int(11) NOT NULL auto_increment,
  `url` varchar(255) collate utf8_bin NOT NULL,
  `md5` varchar(32) collate utf8_bin NOT NULL,
  `host` varchar(255) collate utf8_bin default NULL,
  `content_sha1` varchar(40) collate utf8_bin NOT NULL,
  `add_date` datetime NOT NULL,
  PRIMARY KEY  (`id`),
  UNIQUE KEY `url` (`url`),
  UNIQUE KEY `md5` (`md5`),
  KEY `main_crawl_document_content_sha1` (`content_sha1`),
  KEY `main_crawl_document_discover_date` (`add_date`),
  KEY `main_crawl_document_host` (`host`),
  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

I print out the the lengths of the data I am trying to insert into the table ( I am testing using only one URL ):

len(url) =  89
len(md5) =  32
len(host) =  20
len(content_sha1) =  40
len(add_date) =  19

I was using a cursor created by Django.db.connection. To be more informative, I paste the complete database query command I passed to cursor.execute()

INSERT INTO main_document SET url='ftp://ftp.ncbi.nlm.nih.gov/pub/pmc/0a/39/Arthritis_Res_2000_Jun_5_2%284%29_315-326.tar.gz',md5='b6ba3adde8de87e4dc255092b04d07ea',host='ftp.ncbi.nlm.nih.gov',content_sha1='9aeab4412cc9b1add84a6d2bca574664e193b56e',add_date='2012-05-15 00:00:00';

The funny thing is that, the command above works when I copy and pasted to the MySQL command line. No error messages and the data are just inserted correctly.

What is going wrong?

Answer 1

cursor.execute handles MySQL escaping if you use it correctly. Some Examples Here

The basic idea is to use %s in the raw SQL string where you currently are including the raw values, and then pass a second argument to cursor.execute() which is a tuple (or array) of the values in order. In your case, this would look like:

url = 'ftp://ftp.ncbi.nlm.nih.gov/pub/pmc/0a/39/Arthritis_Res_2000_Jun_5_2%284%29_315-326.tar.gz'
md5 = 'b6ba3adde8de87e4dc255092b04d07ea'
host = 'ftp.ncbi.nlm.nih.gov'
content_sha1 = '9aeab4412cc9b1add84a6d2bca574664e193b56e'
add_date = '2012-05-15 00:00:00'
sql = "INSERT INTO main_document SET url = %s, md5 = %s, host = %s, content_sha1 = %s, add_date = %s"
cursor.execute(sql, (url, md5, host, content_sha1, add_date))