And both MySQL and PostgreSQL have put in work to make ALTER less painful by reducing the situations where a full table rewrite is necessary. In PostgreSQL you

And both MySQL and PostgreSQL have put in work to make ALTER less painful by reducing the situations where a full table rewrite is necessary. In PostgreSQL you can both add and remove columns without the table being rewritten as long as you do not set a default value. You can also increase the lengths of varchars without any rewrite.