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# -*- coding: utf-8 -*-
from __future__ import unicode_literals
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',
default=False, 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(Command, self).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)]
# 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)
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