Database Reference
In-Depth Information
AppendixA.The
Nonrelational
Landscape
Cassandra is one of many new nonrelational database projects that have sprung up recently, and
in order to understand their goals and the designs that have been shaped by those goals, it may
prove useful to take a step back and understand what these different projects are about.
NOTE
We've lately become familiar with the term “NoSQL” to describe a set of databases that don't use
SQL. I have been using the term “nonrelational” in acknowledgment that these databases are frequently
grouped together in the popular imagination. But part of the point of this appendix is to illustrate that
we probably should stop talking this way. It is specious to compare NoSQL databases to relational data-
bases; as you'll see, none of the so-called “NoSQL” databases have the same implementation, goals,
features, advantages, and disadvantages. So comparing “NoSQL” to “relational” is really a shell game.
So in this appendix we review a variety of popular nonrelational databases. Cassandra does cer-
tain things very, very well. It does other things less well. So my aim here is to help you under-
stand Cassandra's place in the constellation of competing nonrelational databases so that you are
best armed to make the right choice of database for your needs. If you already know that you
want to employ Cassandra, this survey should still prove useful in understanding some of the
design decisions and trade-offs made in Cassandra.
Nonrelational Databases
Of course the world is full of popular databases that have never employed anything like a rela-
tional model. These include object databases, XML native databases, document-oriented data-
bases, graph databases, and key-value stores. Some of these represent products that have been
around for many years, and some are just starting to see production use. I examine a few of these
nonrelational databases here.
