Wordpress: add custom meta key to all of the post type

gistfile1

<?php
#domain.com/?run_script=1 to run this script
function add_my_custom_meta_key(){
	global $wpdb;
	if ($_GET['run_script'] =='1' && !is_admin() )
	{
		$q = 'SELECT id from wp_posts where post_type = "MY_CUSTOM_POST_TYPE"';
		$ids = $wpdb->get_col($q);
		foreach($ids as $id)
		{
			$arr = array('post_id' => $id, 'meta_key' => 'MY_KEY_NAME', 'meta_value' => 'MY_VALUE');
			$wpdb->insert( 'wp_postmeta', $arr );
		}
	}
	print 'DONE!';
}

add_action( 'init', 'add_my_custom_meta_key' );