How to use the gear.Database function in gear

async def main():
    scope = sys.argv[1]

    worker_type = 'standard'
    if scope == 'deploy':
        worker_cores = 8
        worker_disk_size_gb = 100
        max_instances = 10
        pool_size = 10
    else:
        worker_cores = 1
        worker_disk_size_gb = 10
        max_instances = 3
        pool_size = 2
        
    db = Database()
    await db.async_init()

    # 22 is 16 bytes of entropy
    # math.log((2**8)**16, 62) = 21.497443706501368
    sigma = string.ascii_letters + string.digits
    instance_id = ''.join([secrets.choice(sigma) for _ in range(22)])

    await db.execute_insertone(
        '''
INSERT INTO globals (
  instance_id, internal_token,
  worker_cores, worker_type, worker_disk_size_gb, max_instances, pool_size)
VALUES (%s, %s, %s, %s, %s, %s, %s);
''',
        (instance_id, secrets.token_urlsafe(32),
         worker_cores, worker_type, worker_disk_size_gb, max_instances, pool_size))

database_name = create_database_config['database_name']
    cant_create_database = create_database_config['cant_create_database']

    if cant_create_database:
        assert sql_config.get('db') is not None

        await write_user_config(namespace, database_name, 'admin', sql_config)
        await write_user_config(namespace, database_name, 'user', sql_config)
        return

    scope = create_database_config['scope']
    _name = create_database_config['_name']
    admin_username = create_database_config['admin_username']
    user_username = create_database_config['user_username']

    db = Database()
    await db.async_init()

    if scope == 'deploy':
        assert _name == database_name

        # create if not exists
        rows = db.execute_and_fetchall(
            "SHOW DATABASES LIKE '{database_name}';")
        rows = [row async for row in rows]
        if len(rows) > 0:
            assert len(rows) == 1
            return

    admin_password = secrets.token_urlsafe(16)
    user_password = secrets.token_urlsafe(16)

async def on_startup(app):
    pool = concurrent.futures.ThreadPoolExecutor()
    app['blocking_pool'] = pool

    db = Database()
    await db.async_init()
    app['db'] = db

    row = await db.select_and_fetchone(
        'SELECT worker_type, worker_cores, instance_id, internal_token FROM globals;')

    app['worker_type'] = row['worker_type']
    app['worker_cores'] = row['worker_cores']

    instance_id = row['instance_id']
    log.info(f'instance_id {instance_id}')
    app['instance_id'] = instance_id

    app['driver_headers'] = {
        'Authorization': f'Bearer {row["internal_token"]}'
    }

out, _ = await check_shell_output(
        f'''
kubectl -n {namespace} get -o json secret {shq(admin_secret_name)}
''')
    admin_secret = json.loads(out)

    with open('/sql-config.json', 'wb') as f:
        f.write(base64.b64decode(admin_secret['data']['sql-config.json']))

    with open('/sql-config.cnf', 'wb') as f:
        f.write(base64.b64decode(admin_secret['data']['sql-config.cnf']))

    os.environ['HAIL_DATABASE_CONFIG_FILE'] = '/sql-config.json'
    os.environ['HAIL_SCOPE'] = scope

    db = Database()
    await db.async_init()

    rows = db.execute_and_fetchall(
        f"SHOW TABLES LIKE '{database_name}_migration_version';")
    rows = [row async for row in rows]
    if len(rows) == 0:
        await db.just_execute(f'''
CREATE TABLE `{database_name}_migration_version` (
  `version` BIGINT NOT NULL
) ENGINE = InnoDB;
INSERT INTO `{database_name}_migration_version` (`version`) VALUES (1);

CREATE TABLE {database_name}_migrations (
  `version` BIGINT NOT NULL,
  `name` VARCHAR(100),
  `script_sha1` VARCHAR(40),

async def on_startup(app):
    pool = concurrent.futures.ThreadPoolExecutor()
    app['blocking_pool'] = pool

    kube.config.load_incluster_config()
    k8s_client = kube.client.CoreV1Api()
    app['k8s_client'] = k8s_client

    db = Database()
    await db.async_init()
    app['db'] = db

    row = await db.select_and_fetchone(
        'SELECT instance_id, internal_token FROM globals;')
    instance_id = row['instance_id']
    log.info(f'instance_id {instance_id}')
    app['instance_id'] = instance_id

    app['internal_token'] = row['internal_token']

    machine_name_prefix = f'batch-worker-{DEFAULT_NAMESPACE}-'

    credentials = google.oauth2.service_account.Credentials.from_service_account_file(
        '/gsa-key/key.json')
    gservices = GServices(machine_name_prefix, credentials)