migrations.py 文件源码

def rollback_migrations():
    lower = -1
    upper = -1
    with database.Cursor() as cursor:
        cursor.prepare("SELECT version FROM __migrations ORDER BY version DESC LIMIT 2")
        cursor.exec_()
        if cursor.next():
            upper = int(cursor.value("version"))
        if cursor.next():
            lower = int(cursor.value("version"))

    should_apply = False

    migration_file, migration_name = tempfile.mkstemp()

    for migration in sorted(os.listdir("../migrations"), reverse=True):
        nb = int(migration.split("_")[0])
        if lower < nb <= upper:
            should_apply = True
            print(f"Rollback {migration}")
            with open(os.path.join("../migrations", migration, "down.sql")) as fd:
                os.write(migration_file, fd.read().encode())

    os.write(migration_file, f"DELETE FROM __migrations WHERE version={upper};\n".encode())

    if should_apply:
        execute_sql_file(migration_name)
    else:
        print("Nothing to do")
    os.remove(migration_name)