@Override
  public long getEstimatedMemorySize() {
    long size = 0;
    size += writeBuffers == null ? 0 : writeBuffers.getEstimatedMemorySize();
    size += unsafeReadPos == null ? 0 : unsafeReadPos.getEstimatedMemorySize();
    return size;
  }
THIS METHOD IS NOT THREAD-SAFE. Use only at load time (or be mindful of thread safety).
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/fast/VectorMapJoinFastKeyStore.java