Tobias Tobias - 1 year ago 107
MySQL Question

Django 1.8 app mysteriously fails with initial migration due to errno: 150 "Foreign key constraint is incorrectly formed"

I'm writing an app in django 1.8 with python 3.4 and I'm encountering an issue with using MySQL as the database backend which has got me completely stumped.

When I start off with a new database and call ./ migrate (or syncdb) and it tries to create the initial database, I get the following traceback:

(virtualenv)~/projects/projmoj (master ✘)✹✭ ᐅ ./ migrate
Operations to perform:
Synchronize unmigrated apps: allauth, rest_framework, registration, rest_auth, projmoj, messages, project, staticfiles
Apply all migrations: contenttypes, sites, sessions, task, auth, admin, authtoken, static_precompiler, account
Synchronizing apps without migrations:
Creating tables...
Creating table project_project
Creating table project_membership
Running deferred SQL...
Traceback (most recent call last):
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/django/db/backends/", line 62, in execute
return self.cursor.execute(sql)
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/django/db/backends/mysql/", line 124, in execute
return self.cursor.execute(query, args)
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 220, in execute
self.errorhandler(self, exc, value)
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 36, in defaulterrorhandler
raise errorvalue
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 209, in execute
r = self._query(query)
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 371, in _query
rowcount = self._do_query(q)
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 335, in _do_query
File "/home/tobbe/projects/projmoj/virtualenv/lib/python3.4/site-packages/MySQLdb/", line 280, in query
_mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1005, 'Can\'t create table `tasks`.`#sql-1c32_9` (errno: 150 "Foreign key constraint is incorrectly formed")')

This error happens when I do the same on a web hosting service, it works however using sqlite on both the hosting service and localhost.

I have no migrations, and these are my models:

class Project(models.Model):
name = models.CharField(max_length = 32)
description = models.TextField(null=True, blank=True)
creation_date = models.DateTimeField(auto_now_add=True)

def get_owner(self):
return self.members.filter(status=OWNER).first().user

def get_membership(self, user):
return self.members.filter(user=user).first()

def __str__(self):
return str( + " - by " + str(self.get_owner().username)

class Membership(models.Model):
user = models.ForeignKey(User, related_name='joined_projects')
project = models.ForeignKey(Project, related_name='members')
status = models.PositiveSmallIntegerField(choices=MEMBER_STATUS)
join_date = models.DateTimeField(auto_now_add=True)

def __str__(self):
return str(self.user.username)

class Sprint(models.Model):
name = models.CharField(max_length = 32, null=True, blank=True)
start_date = models.DateTimeField()
due_date = models.DateTimeField(null=True, blank=True)
project = models.ForeignKey(Project, related_name='sprints')
status = models.PositiveSmallIntegerField(choices=SPRINT_STATUS, default=PLANNING)

def __str__(self):
return str( + " - " + str(self.project)

class Category(models.Model):
name = models.CharField(max_length = 32)
project = models.ForeignKey(Project, related_name='categories')

def __str__(self):
return str( + " - " + str(self.project)

class Goal(models.Model):
name = models.CharField(max_length = 32)
description = models.TextField(null=True, blank=True)
project = models.ForeignKey(Project, related_name='goals')
completion = models.PositiveSmallIntegerField(choices=COMPLETION, default=NOT_COMPLETED)

def __str__(self):
return str( + " - " + str(self.project)

class Task(models.Model):
name = models.CharField(max_length = 64)
description = models.TextField(null=True, blank=True)
project = models.ForeignKey(Project, related_name='tasks')
category = models.ForeignKey(Category, related_name='tasks', null=True, blank=True)
goal = models.ForeignKey(Goal, related_name='tasks', null=True, blank=True)
creation_date = models.DateTimeField(auto_now_add=True)
sprint = models.ForeignKey(Sprint, related_name='tasks', null=True, blank=True)
status = models.PositiveSmallIntegerField(choices=TASK_STATUS, default=WAITING)
dedicated_hours = models.DecimalField(max_digits=6, decimal_places=2, null=True, blank=True)
assigned_worker = models.ForeignKey(User, null=True, blank=True)
priority = models.PositiveSmallIntegerField(choices=PRIORITY, default=NORMAL)

def __str__(self):
return str( + " - " + str(self.project)

class HourReport(models.Model):
task = models.ForeignKey(Task, related_name='hour_reports')
worker = models.ForeignKey(User, related_name='hour_reports')
hours_spent = models.DecimalField(max_digits=6, decimal_places=2)
date = models.DateTimeField(auto_now_add=True)

def __str__(self):
return str(self.hours_spent) + " on " + str(self.task)

My database settings:

'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'tasks',
'USER': 'root',
'PASSWORD': 'mysqlmysql',
'HOST': 'localhost',

Versions etc:

  • Django 1.8

  • Python 3.4

  • Default storage engine: InnoDB

  • Mysqlclient 1.3.6

  • Server: MySQL 5.5.42 on Amazon RDS (at web hosting)

  • Server: 10.0.21-MariaDB-log MariaDB Server (localhost)

When googling it seems like this error is often when people stuff up their manual SQL code, but I am doing it all automatically through django.

Any ideas?

Answer Source

The log is telling you that you have not created migrations for your project app. You should create migrations for the app before running migrate.

./ makemigrations project
./ migrate

Since it's a new database, you'd be better to completely reset it before trying either approach, otherwise you'll have to manually deal with its current inconsistent state.

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