WooCommerce - bulk update order status

woocommerce_bulk_update_order_status.php

$query = new WC_Order_Query( array(
    'limit' => -1,
    'return' => 'ids',
) );
$orders = $query->get_orders();
foreach ( $orders as $order_id ) {
    $order = new WC_Order( $order_id );
    if ( ! empty( $order ) ) {
        $order->update_status( 'processing' );
    }
}