84 lines
3.2 KiB
Python
84 lines
3.2 KiB
Python
from django.apps import apps
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from django.core.management.base import BaseCommand, CommandError
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from django.db import DEFAULT_DB_ALIAS, connections
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from django.db.migrations.loader import AmbiguityError, MigrationLoader
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class Command(BaseCommand):
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help = "Prints the SQL statements for the named migration."
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output_transaction = True
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def add_arguments(self, parser):
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parser.add_argument(
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"app_label", help="App label of the application containing the migration."
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)
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parser.add_argument(
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"migration_name", help="Migration name to print the SQL for."
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)
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parser.add_argument(
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"--database",
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default=DEFAULT_DB_ALIAS,
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help=(
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'Nominates a database to create SQL for. Defaults to the "default" '
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"database."
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),
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)
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parser.add_argument(
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"--backwards",
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action="store_true",
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help="Creates SQL to unapply the migration, rather than to apply it",
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)
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def execute(self, *args, **options):
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# sqlmigrate doesn't support coloring its output but we need to force
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# no_color=True so that the BEGIN/COMMIT statements added by
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# output_transaction don't get colored either.
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options["no_color"] = True
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return super().execute(*args, **options)
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def handle(self, *args, **options):
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# Get the database we're operating from
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connection = connections[options["database"]]
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# Load up a loader to get all the migration data, but don't replace
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# migrations.
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loader = MigrationLoader(connection, replace_migrations=False)
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# Resolve command-line arguments into a migration
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app_label, migration_name = options["app_label"], options["migration_name"]
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# Validate app_label
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try:
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apps.get_app_config(app_label)
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except LookupError as err:
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raise CommandError(str(err))
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if app_label not in loader.migrated_apps:
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raise CommandError("App '%s' does not have migrations" % app_label)
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try:
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migration = loader.get_migration_by_prefix(app_label, migration_name)
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except AmbiguityError:
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raise CommandError(
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"More than one migration matches '%s' in app '%s'. Please be more "
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"specific." % (migration_name, app_label)
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)
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except KeyError:
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raise CommandError(
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"Cannot find a migration matching '%s' from app '%s'. Is it in "
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"INSTALLED_APPS?" % (migration_name, app_label)
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)
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target = (app_label, migration.name)
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# Show begin/end around output for atomic migrations, if the database
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# supports transactional DDL.
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self.output_transaction = (
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migration.atomic and connection.features.can_rollback_ddl
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)
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# Make a plan that represents just the requested migrations and show SQL
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# for it
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plan = [(loader.graph.nodes[target], options["backwards"])]
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sql_statements = loader.collect_sql(plan)
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if not sql_statements and options["verbosity"] >= 1:
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self.stderr.write("No operations found.")
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return "\n".join(sql_statements)
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