Question

First off, here’s my current setup:

Django : version 1.3

MySQL : version 4.0.18 (not my 1st choice…)

When I run syncdb, I get the following error:

Creating tables ...
Creating table auth_permission
Creating table auth_group_permissions
Traceback (most recent call last):
  File "C:\path_to_app\manage.py", line 14, in <module>
    execute_manager(settings)
  File "C:\Python27\lib\site-packages\django\core\management\__init__.py", line 438, in execute_manager
    utility.execute()
  File "C:\Python27\lib\site-packages\django\core\management\__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Python27\lib\site-packages\django\core\management\base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "C:\Python27\lib\site-packages\django\core\management\base.py", line 220, in execute
    output = self.handle(*args, **options)
  File "C:\Python27\lib\site-packages\django\core\management\base.py", line 351, in handle
    return self.handle_noargs(**options)
  File "C:\Python27\lib\site-packages\django\core\management\commands\syncdb.py", line 101, in handle_noargs
    cursor.execute(statement)
  File "C:\Python27\lib\site-packages\django\db\backends\util.py", line 34, in execute
    return self.cursor.execute(sql, params)
  File "C:\Python27\lib\site-packages\django\db\backends\mysql\base.py", line 86, in execute
    return self.cursor.execute(query, args)
  File "C:\Python27\lib\site-packages\MySQLdb\cursors.py", line 174, in execute
    self.errorhandler(self, exc, value)
  File "C:\Python27\lib\site-packages\MySQLdb\connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
_mysql_exceptions.OperationalError: (1005, "Can't create table '.\\database_name\\#sql-d64_e75f2.frm' (errno: 150)")

From what I understand it has something to do with how InnoDB handles foreign keys. Here’s what my setting file looks like:

DATABASES = {
    'default': {
        ....
        'OPTIONS':  { 'init_command': 'SET table_type=INNODB;', 'charset': 'latin1'}, 
    },
}

When “SET table_type=INNODB” is not specfied, everything runs smoothly. I’ve looked around on the net and it seems the InnoDB engine doesn’t like something about the SQL Django is generating

For now, the only work around I found, was tho create the tables myself, and use inspectDB to generate the models…

Is there a fix for this? Thanks!

Answer 1

I traced the source of the problem. When creating 2 InnoDB tables with a foreign key relationship, the foreign key column must be indexed explicitly prior to MySQL 4.1.2. Using Django’s ORM, this can be done by using the db_index=True option in the foreign key field. However, in the Django generated SQL, the CREATE INDEX statement is issued after the foreign key relationship is created. For example, for the following models:

class Customer(models.Model):
    first_name = models.CharField(max_length=100)
    last_name = models.CharField(max_length=100)

class Order(models.Model):
    customer = models.ForeignKey(Customer, db_index=True)

Django generates the following SQL code:

BEGIN;
CREATE TABLE `foo_app_customer` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `first_name` varchar(100) NOT NULL,
    `last_name` varchar(100) NOT NULL
)
;
CREATE TABLE `foo_app_order` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `customer_id` integer NOT NULL
)
;
ALTER TABLE `foo_app_order` ADD CONSTRAINT `customer_id_refs_id_27e4f922` FOREIGN KEY (`customer_id`) REFERENCES `foo_app_customer` (`id`);
CREATE INDEX `foo_app_order_12366e04` ON `foo_app_order` (`customer_id`);
COMMIT;  

If you try running this code using MySQL 4.0, an errno 150 will occur when trying to execute the ALTER TABLE statement. But if the CREATE INDEX statement is issued first, everything works like a charm. As far as I can tell, the only workaround for this is to create your own table manually and using inspectdb afterwards to generate the models.

Also, I created a new Django ticket.