通过修改我发布的链接中的代码，设法解决了这个问题：

function atom_search_where($where){
global $wpdb;
if($_SESSION[\'js\'] != \'\')
$where .= "OR (t.name LIKE \'%".trim($_SESSION[\'js\'])."%\' AND {$wpdb-    >posts}.post_status = \'publish\')";
$where .= "OR ($wpdb->postmeta.meta_key = \'_job_ref\' AND $wpdb->postmeta.meta_value = \'".$_SESSION[\'js\']."\')";
return $where;
}

function atom_search_join($join){
global $wpdb;
if($_SESSION[\'js\'] != \'\')
$join .= "LEFT JOIN {$wpdb->term_relationships} tr ON {$wpdb->posts}.ID = tr.object_id INNER JOIN {$wpdb->term_taxonomy} tt ON tt.term_taxonomy_id=tr.term_taxonomy_id INNER JOIN {$wpdb->terms} t ON t.term_id = tt.term_id";
$join .= "LEFT JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)";
return $join;
}