Woocommerce order admin list custom field filter

wc_order_admin_list_custom_field_filter.php

<?php
//// wc order admin list custom field filter ////
function woo_orders_list_custom_filter($query) {
    $post_type = !empty($_GET['post_type']) ? filter_input(INPUT_GET, 'post_type') : false;
    $lctn = !empty($_GET['lctn']) ? filter_input(INPUT_GET, 'lctn') : false;

    if (is_admin() && ($post_type == 'shop_order' && $query->is_main_query() && $lctn > 0)) {
        $meta = $query->get('meta_query');
        $meta[] = array('key' => 'delivery_name', 'value' => $lctn, 'compare' => '=');
        $query->set('meta_query', $meta);
    }
}

add_action('pre_get_posts', 'woo_orders_list_custom_filter');

add_action('wp_ajax_locationsFilterSelect', 'locationsFilterSelect');

function locationsFilterSelect() {
    global $wpdb;
    $lctn = filter_input(INPUT_POST, 'lctn');

    $out = "<select name='lctn' id='filter_by_location'><option value='0'>All Locations</option>";

    $ids_res = $wpdb->get_results("SELECT DISTINCT pm.meta_value FROM $wpdb->postmeta pm JOIN $wpdb->posts p ON (p.ID = pm.post_id AND p.post_type = 'shop_order') WHERE pm.meta_key = 'delivery_name'");
    if ($ids_res) {
        $ids = array_map(function($e) {
            return $e->meta_value;
        }, $ids_res);
        $posts = $wpdb->get_results("SELECT * FROM $wpdb->posts WHERE ID IN (" . implode(',', $ids) . ") ORDER BY post_title ASC");
        foreach ($posts as $p) {
            $sel = $lctn == $p->ID ? 'selected="selected"' : false;
            $out .= "<option $sel value='$p->ID'>$p->post_title</option>";
        }
    }

    echo $out . "</select>";
    exit();
}

//// end of wc order admin list custom field filter ////

///// js section admin order list ///////
    if ($('.cp-shop_order').length > 0) {
        $.ajax({
            type: "POST",
            url: '/wp-admin/admin-ajax.php',
            data: "action=locationsFilterSelect&lctn="+takeGetParam('lctn'),
            beforeSend: function () {
            },
            success: function (resp) {
                $('#filter-by-date').after(resp);
            }
        });
    }
    /// end of admin order list ///