Unable to generate migrations in Django 1.11 - mysql

Question

On a blank MySQL database, I generated migrations for a Django 1.11 project with:
python manage.py makemigrations
I have several custom inter-dependent apps, but all the migrations generated without error. However, when I tried to apply these migrations with:
python manage.py migrate
it applies most app migrations just fine, but with some custom FeinCMS migrations with:
Applying page.0001_initial...Traceback (most recent call last):
File "manage.py", line 9, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
utility.execute()
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 356, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 204, in handle
fake_initial=fake_initial,
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 115, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 93, in __exit__
self.execute(sql)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 120, in execute
cursor.execute(sql, params)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 101, in execute
return self.cursor.execute(query, args)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 205, in execute
self.errorhandler(self, exc, value)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')
Unfortunately, it doesn't say which foreign key wasn't generated, and the migration has several. I tried commenting out each field in the migration re-running it, but the migration succeeds when I do it that way.
Why is this migration failing and how do I fix it?

Answer 1

You have an issue in Django created tables that table does not have INNODB ENGINE.
In MySql If table has INNODB ENGINE that can make relation as foreign key otherwise Django will return error as mentioned in question
"django.db.utils.IntegrityError: (1215, 'Cannot add foreign key constraint')"
I have solution for this issue.
Firstly create new management command file like name "convert_to_innodb"
and add code as below in that management command file
from django.core.management.base import BaseCommand
from django.db import connections
class Command(BaseCommand):
def handle(self, database="default", *args, **options):
cursor = connections[database].cursor()
cursor.execute("SHOW TABLE STATUS")
for row in cursor.fetchall():
if row[1] != "InnoDB":
print "Converting %s" % row[0],
print cursor.execute("ALTER TABLE %s ENGINE=INNODB" % row[0])
and RUN command in terminal
python manage.py convert_to_innodb
After this command execution you can make foreign key in already created table but
'OPTIONS': {
'init_command': 'SET default_storage_engine=INNODB',
}
add this configuration in DATABASE settings like below
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
'NAME': 'DB_NAME',
'USER': 'DB_USER',
'PASSWORD': 'DB_PASSWORD',
'HOST': 'localhost', # Or an IP Address that your DB is hosted on
'PORT': '3306',
'OPTIONS': {
'init_command': 'SET default_storage_engine=INNODB',
}
}
}
This db configuration will create next time INNODB ENGINE table that will work for future without errors

Answer 2

Because of a bad merge, there were some errors in previous migrations, causing a disconnect between older migrations and the columns in my models. I fixed this by:
deleting all my migrations
truncating my django_migrations table
running manage.py makemigrations
Then migrate worked.