I think the one clean SQL bolted onto NoSQL that I've seen is spark. Since spark treats the NoSQL as having a structure that matches the underlying database, bu

I think the one clean SQL bolted onto NoSQL that I've seen is spark. Since spark treats the NoSQL as having a structure that matches the underlying database, but it also runs an SQL layer, it's kind of an interesting way to do it. Now that's also up to the spark "driver" like for mongodb - the driver code has to tell mongo to give it some "shape" for the collection otherwise spark can't work with it. Now it's likely to have a shape, but the driver may skip a random column if it's not present enough.