We are working on the Pig Logical Optimizer, and running into some
difficulty navigating the plan.
If we run explain on a query with a CoGroup, we get something like:
Cogroup
| |
| |-- Project [0]
|
|------ ForEach
| <etc>
What we want to do is determine that this particular Cogroup operates on a
projection of field 0.
If we create a new LogicalTransformer that is applied to Cogroup operators,
and call
mPlan.getPredecessors(ourCogroupOperator) , we only get the ForEach.
Calling getSuccessors results in a null being returned (Cogroup is indeed
the root).
How do we find the Project operator above? What is its relationship,
plan-wise, with the Cogroup operator?
Thanks a lot,
Dmitriy Ryaboy, Ashutosh Chauhan, Tejal Desai
