from django.core.management.base import BaseCommand, CommandError from django.db import DEFAULT_DB_ALIAS, connections from django.db.migrations.executor import MigrationExecutor from django.db.migrations.loader import AmbiguityError class Command(BaseCommand): help = "Prints the SQL statements for the named migration." output_transaction = True def add_arguments(self, parser): parser.add_argument('app_label', help='App label of the application containing the migration.') parser.add_argument('migration_name', help='Migration name to print the SQL for.') parser.add_argument( '--database', default=DEFAULT_DB_ALIAS, help='Nominates a database to create SQL for. Defaults to the "default" database.', ) parser.add_argument( '--backwards', action='store_true', dest='backwards', help='Creates SQL to unapply the migration, rather than to apply it', ) def execute(self, *args, **options): # sqlmigrate doesn't support coloring its output but we need to force # no_color=True so that the BEGIN/COMMIT statements added by # output_transaction don't get colored either. options['no_color'] = True return super().execute(*args, **options) def handle(self, *args, **options): # Get the database we're operating from connection = connections[options['database']] # Load up an executor to get all the migration data executor = MigrationExecutor(connection) # Resolve command-line arguments into a migration app_label, migration_name = options['app_label'], options['migration_name'] if app_label not in executor.loader.migrated_apps: raise CommandError("App '%s' does not have migrations" % app_label) try: migration = executor.loader.get_migration_by_prefix(app_label, migration_name) except AmbiguityError: raise CommandError("More than one migration matches '%s' in app '%s'. Please be more specific." % ( migration_name, app_label)) except KeyError: raise CommandError("Cannot find a migration matching '%s' from app '%s'. Is it in INSTALLED_APPS?" % ( migration_name, app_label)) targets = [(app_label, migration.name)] # Show begin/end around output only for atomic migrations self.output_transaction = migration.atomic # Make a plan that represents just the requested migrations and show SQL # for it plan = [(executor.loader.graph.nodes[targets[0]], options['backwards'])] sql_statements = executor.collect_sql(plan) return '\n'.join(sql_statements)