Clojure Cookbook

Chapter 6. Databases

6.0. Introduction

Storing data in a database is not an uncommon task for developers—in this day and age, it’s practically a given. As with nearly every language under the sun, there is a bevy of drivers and clients to interact with databases from Clojure. What sets Clojure apart, however, is its ability to compose.

As we’ve said before in this book: in Clojure, data is king. You’ll find many of the database client libraries do a little legwork to connect you to the datastore, then promptly get out of your way. Such libraries don’t do so out of laziness (at least, we hope), but rather out of the principle of separation of concerns: I’ll handle connecting to the database; you handle the domain (your data). In fact, the best APIs are built out of data, providing only one or two functions and letting you manipulate queries and data to be inserted directly as Clojure data structures.

In this chapter, we’ll visit a wide number of databases and techniques, including the SQLs, full-text search, Mongo, Redis, and Datomic.

Datomic is one of the more interesting recent developments in the database landscape. Invented and maintained by Rich Hickey (who you will probably recognize as the same person who wrote Clojure itself), it is a scalable, transactional, value-oriented, time-aware database built around the same principles and philosophies as Clojure. If you like Clojure, you should definitely give Datomic a try, both as your application’s datastore and also as a learning ...