@Override
  public void evaluate(VectorizedRowBatch batch) throws HiveException {

    if (childExpressions != null) {
      super.evaluateChildren(batch);
    }

    BytesColumnVector inputColVector = (BytesColumnVector) batch.cols[inputColumnNum[0]];
    int[] sel = batch.selected;
    int n = batch.size;
    LongColumnVector outputColVector = (LongColumnVector) batch.cols[outputColumnNum];

    boolean[] inputIsNull = inputColVector.isNull;
    boolean[] outputIsNull = outputColVector.isNull;

    if (n == 0) {

      // Nothing to do
      return;
    }

    // We do not need to do a column reset since we are carefully changing the output.
    outputColVector.isRepeating = false;

    if (inputColVector.isRepeating) {
      if (inputColVector.noNulls || !inputIsNull[0]) {
        // Set isNull before call in case it changes it mind.
        outputIsNull[0] = false;
        func(outputColVector, inputColVector, 0);
      } else {
        outputIsNull[0] = true;
        outputColVector.noNulls = false;
      }
      outputColVector.isRepeating = true;
      return;
    }

    if (inputColVector.noNulls) {
      if (batch.selectedInUse) {

        // CONSIDER: For large n, fill n or all of isNull array and use the tighter ELSE loop.

        if (!outputColVector.noNulls) {
          for(int j = 0; j != n; j++) {
           final int i = sel[j];
           // Set isNull before call in case it changes it mind.
           outputIsNull[i] = false;
           func(outputColVector, inputColVector, i);
         }
        } else {
          for(int j = 0; j != n; j++) {
            final int i = sel[j];
            func(outputColVector, inputColVector, i);
          }
        }
      } else {
        if (!outputColVector.noNulls) {

          // Assume it is almost always a performance win to fill all of isNull so we can
          // safely reset noNulls.
          Arrays.fill(outputIsNull, false);
          outputColVector.noNulls = true;
        }
        for(int i = 0; i != n; i++) {
          func(outputColVector, inputColVector, i);
        }
      }
    } else  /* there are NULLs in the inputColVector */ {

      /*
       * Do careful maintenance of the outputColVector.noNulls flag.
       */

      if (batch.selectedInUse) {
        for(int j = 0; j != n; j++) {
          int i = sel[j];
          if (!inputColVector.isNull[i]) {
            // Set isNull before call in case it changes it mind.
            outputColVector.isNull[i] = false;
            func(outputColVector, inputColVector, i);
          } else {
            outputColVector.isNull[i] = true;
            outputColVector.noNulls = false;
          }
        }
      } else {
        for(int i = 0; i != n; i++) {
          if (!inputColVector.isNull[i]) {
            // Set isNull before call in case it changes it mind.
            outputColVector.isNull[i] = false;
            func(outputColVector, inputColVector, i);
          } else {
            outputColVector.isNull[i] = true;
            outputColVector.noNulls = false;
          }
        }
      }
    }
  }
Convert input string to a long, at position i in the respective vectors.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/CastStringToLong.java