Object getEvaluatorResult(VectorPTFEvaluatorBase evaluator) {
      return evaluator.isGroupResultNull() ? null : evaluator.getGroupResult();
    }
Creates a block iterator for a specific range.

@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFGroupBatches.java