public boolean isOnDisk(int partitionId) {
    return hashPartitions[partitionId].hashMapOnDisk;
  }
Check if the hash table of a specified partition is on disk (or "spilled" on creation)
@param partitionId partition number
@return true if on disk, false if in memory
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/HybridHashTableContainer.java