public List<String> getAbortReasons() {
      return abortReasons;
    }
Start to exploit Job Flow Correlation from op.
Example: here is the operator tree we have ...
      JOIN2
     /    \
    RS4   RS5
   /        \
  GBY1     JOIN1
   |       /    \
  RS1     RS2   RS3
The op will be RS4. If we can execute GBY1, JOIN1, and JOIN2 in
the same reducer. This method will return [RS1, RS2, RS3].
@param op
@param correlationCtx
@param correlation
@return
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/optimizer/correlation/CorrelationOptimizer.java