from django.apps import apps from django.core.management.base import BaseCommand, CommandError from django.db import DEFAULT_DB_ALIAS, connections from django.db.migrations.loader import AmbiguityError, MigrationLoader 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", 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 a loader to get all the migration data, but don't replace # migrations. loader = MigrationLoader(connection, replace_migrations=False) # Resolve command-line arguments into a migration app_label, migration_name = options["app_label"], options["migration_name"] # Validate app_label try: apps.get_app_config(app_label) except LookupError as err: raise CommandError(str(err)) if app_label not in loader.migrated_apps: raise CommandError("App '%s' does not have migrations" % app_label) try: migration = 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) ) target = (app_label, migration.name) # Show begin/end around output for atomic migrations, if the database # supports transactional DDL. self.output_transaction = ( migration.atomic and connection.features.can_rollback_ddl ) # Make a plan that represents just the requested migrations and show SQL # for it plan = [(loader.graph.nodes[target], options["backwards"])] sql_statements = loader.collect_sql(plan) if not sql_statements and options["verbosity"] >= 1: self.stderr.write("No operations found.") return "\n".join(sql_statements)