@Override
  public long getEstimatedMemorySize() {
    long size = 0;
    size += writeBuffers == null ? 0 : writeBuffers.getEstimatedMemorySize();
    return size;
  }
@param refWord
@param valueBytes
@param valueStart
@param valueLength
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/fast/VectorMapJoinFastBytesHashMapStore.java