[bzz01]

While all maps like this tend to make little practical sense since they inevitably over-generalize and over-simplify things, I'd still like to point out that they got "columnar" category quite wrong: neither HBase nor Cassandra are columnar stores in a way this term is commonly understood.

HBase and Cassandra still store data in rows, however rows can be partitioned into column families which may be stored separately. Columnar databases are usually also relational (Vertica and Redshift) and support SQL or SQL-like query language.

Anyway, I think regardless of how you define columnar, HBase and Redshift shouldn't end up in the same category as they are quite different in a way they work, throughput/latency and read/write balance and use cases.

[ddrum001]

You're correct that it's very difficult to balance between giving an overview and over-simplifying. We intended this to be a starting point, knowing that we'd have to make a trade-off between including more details and giving a concise overview.

For NoSQL specifically, it's difficult to put every database in only a few categories. We discussed that Cassandra and HBase are "maps of maps" in the details, and we definitely didn't want to imply that they have the same model or use-cases as Redshift. Perhaps our next iteration will explain the "column family" more and include a separate category for the databases that were inspired by the Big Table data model.