Remove post meta keys

I found this from just a Google search (Source)

You have to change met value keys as you want. However, it is highly recommend to take a DB backup before running this code.

<?php
function delete_useless_post_meta() {
   global $wpdb;
   $table = $wpdb->prefix.'postmeta';
   $wpdb->delete ($table, array('meta_key' => '_edit_last'));
   $wpdb->delete ($table, array('meta_key' => '_edit_lock'));
   $wpdb->delete ($table, array('meta_key' => '_wp_old_slug')); }
add_action('wp_logout','delete_useless_post_meta');
?>