The cycles are longer than you're imagining. Relational database folk have been railing against the incursions of one generation of non-relational database type or another since at least the 1980's.
Actually, relational databases are the relative newcomers. The limitations of things like CODASYL were well known to 1960s programmers and Codd's relational model sought to address them.
Why the non-relational databases keep getting reinvented has been a bit of a mystery when there is already a rich history of development to look to. I get the feeling a lot of the industry isn't much into history, especially of pre-micro computer systems.
Network databases, key-value stores, graph databases, commercial offerings like Pick... you'd think the NoSQL people would have looked into it all before proclaiming their new found solutions, but apparently not.
Why the non-relational databases keep getting reinvented has been a bit of a mystery when there is already a rich history of development to look to. I get the feeling a lot of the industry isn't much into history, especially of pre-micro computer systems.
Network databases, key-value stores, graph databases, commercial offerings like Pick... you'd think the NoSQL people would have looked into it all before proclaiming their new found solutions, but apparently not.