private static void findBucketingSortingColumns(List<ExprNodeDesc> exprs,
      List<ColumnInfo> colInfos, List<BucketCol> bucketCols, List<SortCol> sortCols,
      BucketCol[] newBucketCols, SortCol[] newSortCols) {
    findBucketingSortingColumns(exprs, colInfos, bucketCols, sortCols, newBucketCols,
        newSortCols, 0);
  }
If the list of output sort columns has been populated and every column has at least
one representative in the output they can be inferred

@param bctx - BucketingSortingCtx containing inferred columns
@param op - The operator we are inferring information about the output of
@param newSortCols - An array of columns on which the output is sorted, e.g. as output by
                       the method findBucketingSortingColumns
ql/src/java/org/apache/hadoop/hive/ql/optimizer/physical/BucketingSortingOpProcFactory.java