public List<SortCol> getSortedCols(Operator<? extends OperatorDesc> op) {
    return sortedColsByOp.get(op);
  }
This class contains the bucketing sorting context that is passed
while walking the operator tree in inferring bucket/sort columns. The context
contains the mappings from operators and files to the columns their output is
bucketed/sorted on.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/physical/BucketingSortingCtx.java