public static List<String> createOutputColumnNames(List<ExprNodeDesc> expressionList){
    List<String> outputCols = new ArrayList<String>();
    for (int i = 0; i < expressionList.size(); i++) {
      outputCols.add("_col" + i);
    }
    return outputCols;
  }
@param expressionList
@return A list of columns named _colX where x is a number
ql/src/test/org/apache/hadoop/hive/ql/testutil/OperatorTestUtils.java