WordPress 技巧：改进 404 页面跳转到正确的页面的效率

//解决日志改变 post type 之后跳转错误的问题，
add_action( 'template_redirect', 'wpjam_old_slug_redirect');
function wpjam_old_slug_redirect() {
    global $wp_query;
    if ( is_404() && '' != $wp_query->query_vars['name'] ) :
        global $wpdb;

        $query = $wpdb->prepare("SELECT post_id FROM $wpdb->postmeta WHERE meta_key = '_wp_old_slug' AND meta_value = %s", $wp_query->query_vars['name']);

        $id = (int) $wpdb->get_var($query);

        if ( !$id ){
            $link = wpjam_redirect_guess_404_permalink();
        }else{
            $link = get_permalink($id);
        }

        if ( !$link )
            return;

        wp_redirect( $link, 301 );
        exit;
    endif;
}

function wpjam_redirect_guess_404_permalink() {
    global $wpdb, $wp_rewrite;

    if ( get_query_var('name') ) {
        $where = $wpdb->prepare("post_name LIKE %s", like_escape( get_query_var('name') ) . '%');

        $post_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE $where AND post_status = 'publish'");
        if ( ! $post_id )
            return false;
        if ( get_query_var( 'feed' ) )
            return get_post_comments_feed_link( $post_id, get_query_var( 'feed' ) );
        elseif ( get_query_var( 'page' ) )
            return trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( get_query_var( 'page' ), 'single_paged' );
        else
            return get_permalink( $post_id );
    }

    return false;
}