A lot of SQL databases can definitely adhoc determine if indices are necessary; it's just not the default because predictable performance and explicit indices t

A lot of SQL databases can definitely adhoc determine if indices are necessary; it's just not the default because predictable performance and explicit indices tend to be preferred. Postgresql has a handful of plugins that can tell you if you had an indice; would it be used and you can see query plans before/after without actually having to add indices until you're comfortable. This same plugin could easily automate indice creation, but most people don't.