Check for pending Django migrations

问题:

In Django, is there an easy way to check whether all database migrations have been run? I've found manage.py migrate --list, which gives me the information I want, but the format isn't very machine readable.

For context: I have a script that shouldn't start running until the database has been migrated. For various reasons, it would be tricky to send a signal from the process that's running the migrations. So I'd like to have my script periodically check the database to see if all the migrations have run.

回答1:

Shell

The only simple solution I've found so far is running

./manage.py showmigrations | grep '\[ \]'

which will output an empty string in case all migrations have been applied.

However, it is closely tied to the output format.

Python

I checked the source code of migrate command and it seems like this should do the trick:

from django.db.migrations.executor import MigrationExecutor
from django.db import connections, DEFAULT_DB_ALIAS


def is_database_synchronized(database):
    connection = connections[database]
    connection.prepare_database()
    executor = MigrationExecutor(connection)
    targets = executor.loader.graph.leaf_nodes()
    return False if executor.migration_plan(targets) else True

# Usage example.
if is_database_synchronized(DEFAULT_DB_ALIAS):
    # All migrations have been applied.
    pass
else:
    # Unapplied migrations found.
    pass

回答2:

1.10 release notes:

The new makemigrations --check option makes the command exit with a non-zero status when model changes without migrations are detected.

回答3:

Try,

python manage.py migrate --list | grep "\[ \]\|^[a-z]" | grep "[ ]" -B 1

returns,

<app_1>
 [ ] 0001_initial
 [ ] 0002_auto_01201244
 [ ] 0003_auto_12334333

<app_2>
 [ ] 0031_auto_12344544
 [ ] 0032_auto_45456767
 [ ] 0033_auto_23346566

<app_3>
 [ ] 0008_auto_3446677

Update:

If you have updated Django version >= 1.11, use below command,

python manage.py showmigrations | grep '\[ \]\|^[a-z]' | grep '[  ]' -B 1

回答4:

./manage.py showmigrations #check which already-made migrations have been applied or not
(or: ./manage.py showmigrations someApp #for specific app alone)

./manage.py makemigrations --dry-run #check for migrations to be made
(or: ./manage.py makemigrations someApp --dry-run #for specific app alone)

./manage.py makemigrations #make the migrations
(or: ./manage.py makemigrations someApp #for specific app alone)

./manage.py showmigrations #check which already-made migrations have been applied or not
(or: ./manage.py showmigrations someApp #for specific app alone)

./manage.py sqlmigrate someApp 0001 #view SQL changes for specific app & migration

./manage.py migrate #apply migrations
(or: ./manage.py migrate someApp #for specific app alone)

./manage.py showmigrations #check which already-made migrations have been applied or not
(or: ./manage.py showmigrations someApp #for specific app alone)

./manage.py makemigrations --dry-run #check for migrations to be made
(or: ./manage.py makemigrations someApp --dry-run #for specific app alone)

PS:
./manage.py migrate someApp zero #unapply all migrations for specific app

回答5:

Using @Ernest code, I've written a manage_custom.py for pending migrations. You can get the list of pending migrations also migrate those pending migrations (only), hence saving your time.

manage_custom.py

__author__ = "Parag Tyagi"

# set environment
import os
import sys
import django
sys.path.append('../')
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'settings')
django.setup()

from django.core.management import execute_from_command_line
from django.db import DEFAULT_DB_ALIAS, connections
from django.db.migrations.executor import MigrationExecutor


class Migration(object):
    """
    A custom manage.py file for managing pending migrations (only)
    """

    def __init__(self, migrate_per_migration_id=False):
        """
        :param migrate_per_migration_id: Setting this to `True` will migrate each pending migration of any
        particular app individually. `False` will migrate the whole app at a time.

        You can add more arguments (viz. showmigrations, migrate) by defining the argument with prefix as 'ARGV_'
        and create its functionality accordingly.
        """
        self.ARG_PREFIX = 'ARGV_'
        self.MIGRATE_PER_MIGRATION_ID = migrate_per_migration_id
        self.ARGV_showmigrations = False
        self.ARGV_migrate = False

    @staticmethod
    def get_pending_migrations(database):
        """
        :param database: Database alias
        :return: List of pending migrations
        """
        connection = connections[database]
        connection.prepare_database()
        executor = MigrationExecutor(connection)
        targets = executor.loader.graph.leaf_nodes()
        return executor.migration_plan(targets)

    def check_arguments(self, args):
        """
        Method for checking arguments passed while running the command
        :param args: Dictionary of arguments passed while running the script file
        :return: Set the argument variable ('ARGV_<argument>') to True if found else terminate the script
        """
        required_args = filter(None, [var.split(self.ARG_PREFIX)[1] if var.startswith(self.ARG_PREFIX)
                                      else None for var in self.__dict__.keys()])
        if any(k in args for k in required_args):
            for arg in required_args:
                if arg in args:
                    setattr(self, '{}{}'.format(self.ARG_PREFIX, arg), True)
                    break
        else:
            print ("Please pass argument: {}"
                   "\ne.g. python manage_custom.py {}".format(required_args, required_args[0]))
            sys.exit()

    def do_migration(self):
        """
        Migrates all the pending migrations (if any)
        """
        pending_migrations = self.get_pending_migrations(DEFAULT_DB_ALIAS)
        if pending_migrations:
            done_app = []
            for mig in pending_migrations:
                app, migration_id = str(mig[0]).split('.')
                commands = ['manage.py', 'migrate'] + ([app, migration_id] if self.MIGRATE_PER_MIGRATION_ID else [app])
                if self.ARGV_migrate and (app not in done_app or self.MIGRATE_PER_MIGRATION_ID):
                    execute_from_command_line(commands)
                    done_app.append(app)
                elif self.ARGV_showmigrations:
                    print (str(mig[0]))
        else:
            print ("No pending migrations")


if __name__ == '__main__':
    args = sys.argv
    migration = Migration()
    migration.check_arguments(args)
    migration.do_migration()

Usage:

# below command will show all pending migrations
python manage_custom.py showmigrations

# below command will migrate all pending migrations
python manage_custom.py migrate

PS: Please setup environment as per your project structure.

回答6:

Here is my Python soloution to get some information about the migration-states:

from io import StringIO  # for Python 2 use from StringIO import StringIO  
from django.core.management import call_command 

def get_migration_state():
    result = []
    out = StringIO()
    call_command('showmigrations', format="plan", stdout=out)
    out.seek(0)
    for line in out.readlines():
        status, name = line.rsplit(' ', 1)
        result.append((status.strip() == '[X]', name.strip()))
    return result

The result of this function looks like that:

[(True, 'contenttypes.0001_initial'),
 (True, 'auth.0001_initial'),
 (False, 'admin.0001_initial'),
 (False, 'admin.0002_logentry_remove_auto_add')]

Maybe it helps some of you guys..

回答7:

i check it by look up at database at table django_migrations witch store all applied migrations