I thought most of this already exists, just not on the free databases. Having XML or JSON columns that can their interior fields indexed, would replicate what

I thought most of this already exists, just not on the free databases. Having XML or JSON columns that can their interior fields indexed, would replicate what document databases do. Also what having a master-master relational database with a bunch of materialized views replicate what people are using Cassandra for. Is it just because the free databases don't have materialized view support?