public int getLastRowIndex() {
      return (int) (startRowIndex[0] + spillRowCount - 1);
    }
<pre>
Deserializer needs to know which columns to put the deserialized values into. Basically,
deserialization can happen in 2 cases:
1. final read: deserialized values should go back into
the proper output columns in the overflow batch, the mapping is stored in
bufferedColumnMap.
2. "intermediate" read: deserialized values should be just put back into
columns in the same order as they arrived to the serializer (like: [0, 1, 2, 3, 4, 5]
</pre>
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorSpillBlockContainer.java