public Object computeValue(Object row) throws HiveException {
    Object o = expressionDef.getExprEvaluator().evaluate(row);
    return ObjectInspectorUtils.copyToStandardObject(o, expressionDef.getOI());
  }
Uses cache to lookup row value. Computes it on the fly on cache miss.
@param r
@param p
@return row value.
@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/udf/ptf/ValueBoundaryScanner.java