How to do outer join on two columns in Pig Latin
The above answer is actually an INNER join, the correct pig statement should be:
join a by (id, name) LEFT OUTER, b by (id, name)
Answering the question myself -
join a by (id, name), b by (id, name) http://ofps.oreilly.com/titles/9781449302641/advanced_pig_latin.html