private static void setString(BytesColumnVector outputColVector, int i, Text t) {
    if (t == null) {
      outputColVector.noNulls = false;
      outputColVector.isNull[i] = true;
      return;
    }
    outputColVector.setVal(i, t.getBytes(), 0, t.getLength());
  }
Expression for vectorized evaluation of unary UDFs on strings.
An object of {@link IUDFUnaryString} is applied to every element of
the vector.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/StringUnaryUDF.java