> But after contemplating it, is this really necessary?
No, you could always do the materialized equivalent via triggers, so it's not necessary for correctness. And since this feature is limited to the materialized form, too, it doesn't offer much change other than simpler expression of what is going on (which, to be fair, is a big win.)
> I fear for putting business logic and meanings into the wrong the layer
If you don't have some mechanism for calculated columns, you are forced to put domain logic that belongs in the DB in the app layer, which is especially problematic in the (increasingly out of fashion, apparently) circumstance where there are multiple consumers of a DB, as it promotes inconsistency.
No, you could always do the materialized equivalent via triggers, so it's not necessary for correctness. And since this feature is limited to the materialized form, too, it doesn't offer much change other than simpler expression of what is going on (which, to be fair, is a big win.)
> I fear for putting business logic and meanings into the wrong the layer
If you don't have some mechanism for calculated columns, you are forced to put domain logic that belongs in the DB in the app layer, which is especially problematic in the (increasingly out of fashion, apparently) circumstance where there are multiple consumers of a DB, as it promotes inconsistency.