Hi Wilson! You can start by mocking an outer join operator using a special CoGroup function. If one of the two sides for a group is empty, you have the case where you need to append null values. Otherwise, you build the Cartesian produce within the group.
For a proper through-the-stack implementation (not sure if that is needed, but may be nice to have), have a look here: http://flink.incubator.apache.org/docs/0.7-incubating/internal_add_operator.html Greetings, Stephan On Sat, Dec 13, 2014 at 3:19 AM, Zihong Cao <wilsonca...@gmail.com> wrote: > > Hi, > > I am trying to pick up the outer join operator. However, as Fabian > mentioned to me, that this task would require to touch many different > components of the system, it would be a challenge job for me. Therefore I > would need some help:-) > > I might need to walk through some features like Compiler/Optimizer and > Runtime(as Fabian mentioned to me), so where should I start to get familiar? > > One more thing, is the outer join operator implementation similar to the > pure join operator? > > Best, > Wilson Cao
