set the stock status for all products in your WooCommerce store

woocommerce_update_stock_status.php

<?php

/**
 * set the stock status for all products in your WooCommerce store
 * @return void
 */
function woocommerce_update_stock_status(){
  global $wpdb;

	// set all status for products with 0 or less stocked quantity
	$sql = "UPDATE $wpdb->postmeta stock, (SELECT DISTINCT post_id FROM $wpdb->postmeta WHERE meta_key = '_stock' AND meta_value < 1 ) id SET stock.meta_value = 'outofstock' WHERE stock.post_id = id.post_id AND stock.meta_key = '_stock_status';";

	// set all status for products with stock.
	$sql .= "UPDATE $wpdb->postmeta stock, (SELECT DISTINCT post_id FROM $wpdb->postmeta WHERE meta_key = '_stock' AND meta_value > 0 ) id SET stock.meta_value = 'outofstock' WHERE stock.post_id = id.post_id AND stock.meta_key = '_stock_status';";

	// run queries
	$wpdb->query( $sql );
}