public void dumpStats() {
    int numPartitionsInMem = 0;
    int numPartitionsOnDisk = 0;

    for (HashPartition hp : hashPartitions) {
      if (hp.isHashMapOnDisk()) {
        numPartitionsOnDisk++;
      } else {
        numPartitionsInMem++;
      }
    }

    LOG.info("In memory partitions have been processed successfully: " +
        numPartitionsInMem + " partitions in memory have been processed; " +
        numPartitionsOnDisk + " partitions have been spilled to disk and will be processed next.");
  }
Sometimes, when container is empty in multi-table mapjoin, we need to add a dummy row.
This container does not normally support adding rows; this is for the dummy row.
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/HybridHashTableContainer.java