protected void commonSetup() throws HiveException {

    /*
     * Make sure big table BytesColumnVectors have room for string values in the overflow batch...
     */
    for (int column: bigTableByteColumnVectorColumns) {
      BytesColumnVector bytesColumnVector = (BytesColumnVector) overflowBatch.cols[column];
      bytesColumnVector.initBuffer();
    }

    for (int column : nonOuterSmallTableKeyByteColumnVectorColumns) {
      BytesColumnVector bytesColumnVector = (BytesColumnVector) overflowBatch.cols[column];
      bytesColumnVector.initBuffer();
    }

    for (int column : outerSmallTableKeyByteColumnVectorColumns) {
      BytesColumnVector bytesColumnVector = (BytesColumnVector) overflowBatch.cols[column];
      bytesColumnVector.initBuffer();
    }

    for (int column: smallTableByteColumnVectorColumns) {
      BytesColumnVector bytesColumnVector = (BytesColumnVector) overflowBatch.cols[column];
      bytesColumnVector.initBuffer();
    }

    batchCounter = 0;
    rowCounter = 0;
  }
This override lets us substitute our own fast vectorized hash table loader.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/VectorMapJoinCommonOperator.java