In the Distributed processing with Cascalog and Hadoop recipe, we started looking at how to query data in Cascalog with a couple of small examples. However, Cascalog's query language is much more powerful than we saw there. We'll dive in further in this recipe and start looking at some of the logical predicates available. Recipes later in this chapter will have still more examples of querying with Cascalog.
For this recipe, we'll need the project.clj
file dependencies and imports from the Distributed processing with Cascalog and Hadoop recipe. We'll also use the data from that recipe: the sequences of information about the companions and actors from the British television program, Doctor Who.