So far we've seen very basic Cascalog predicates and queries. We've seen queries that pull data from one source generator and maybe include one predicate test. In this recipe, we'll see several more complex queries.
For this recipe, we'll need the dependencies from the Distributed processing with Cascalog and Hadoop recipe. We'll also use the Doctor Who companion data that we defined in that recipe. The source code for this data is available in the code for the book, and you can also download just the code to create this dataset from http://www.ericrochester.com/clj-data-analysis/data/companions.clj.
We'll start with simple queries and build up from there.
First, let's look at a simple join:
user=> (?<- (stdout) [?name ?dr] (full-name ?c ?name) (doctor ?c ?dr)) … RESULTS ----------------------- Ace 7 Adam Mitchell 9 Adelaide Brooke 10 Adric 4 Adric 5 Amy Pond 11 Astrid Peth 10 …
This pulls each companion...