Viewing file:  sqlmigrate.py (3.03 KB) -rw-r--r--
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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 an 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)
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