function wc_update_241_variations() {
	global $wpdb;

	// Select variations that don't have any _stock_status implemented on WooCommerce 2.2.
	$update_variations = $wpdb->get_results(
		"SELECT DISTINCT posts.ID AS variation_id, posts.post_parent AS variation_parent
		FROM {$wpdb->posts} as posts
		LEFT OUTER JOIN {$wpdb->postmeta} AS postmeta ON posts.ID = postmeta.post_id AND postmeta.meta_key = '_stock_status'
		WHERE posts.post_type = 'product_variation'
		AND postmeta.meta_value IS NULL"
	);

	foreach ( $update_variations as $variation ) {
		// Get the parent _stock_status.
		$parent_stock_status = get_post_meta( $variation->variation_parent, '_stock_status', true );

		// Set the _stock_status.
		add_post_meta( $variation->variation_id, '_stock_status', $parent_stock_status ? $parent_stock_status : 'instock', true );

		// Delete old product children array.
		delete_transient( 'wc_product_children_' . $variation->variation_parent );
	}

	// Invalidate old transients such as wc_var_price.
	WC_Cache_Helper::get_transient_version( 'product', true );
}