How and when to update a MySQL index?

I'm using this SQL query to create an index:

    $query = "CREATE INDEX id_index2
            ON countries(geoname_id, name)";

How do I update the index when new entries are added?

Should I run a PHP script with the update query in CRON and run it every nig开发者_开发问答ht?

Is this best practice for automated index updating?

Indexes are updated by MySQL automatically as you insert/update rows. (This may be a performance hitter for huge websites, but you probably aren't running a huge one :).) You don't need to do anything after the initial creation.

It will be automatically updated after adding rows, No need to run any update statements.