From Secrets of BackType’s Data Engineers:
Cascalog is one of their secret weapons, a Clojure-based query language for Hadoop that makes it simple for them to analyze their data in new ways. Inspired by the venerable Datalog, and built on top of Cascading, it allows you to write queries in Clojure and define even complex operations in simple code. Unlike alternatives like Pig or Hive, it’s written within a general-purpose language, so there’s no need for separate user-defined functions, but it’s still a highly-structured way of defining queries.
It’s worthy of note that Cascalog is a distant child of cascading-clojure, created and used by FlightCaster. FlightCaster was acquired this week.