WordPress: Custom Field URL parameter

<?php
//in the functions.php

add_action('parse_request','oldsite_redirect',0);  // 0=before (most) 'parse_request' calls
function oldsite_redirect() {
  if (isset($_GET['lid'])) {
    global $wpdb;
    $sql = "SELECT post_id FROM {$wpdb->postmeta} " .
           "WHERE meta_key='lid' AND meta_value='%s'";
    $sql = $wpdb->prepare($sql,$_GET['lid']);
    $post_id = $wpdb->get_var($sql);
    if ($post_id) {
      $permalink = get_permalink($post_id);
      if ($permalink) {
        wp_safe_redirect($permalink,301);
        exit;
      }
    }
  }
}