protected final int computeMurmurHash(HiveKey firstKey) {
    return Murmur3.hash32(firstKey.getBytes(), firstKey.getDistKeyLength(), 0);
  }
Populate distinct keys part of cachedKeys for a particular row.
@param row the row
@param index the cachedKeys index to write to
ql/src/java/org/apache/hadoop/hive/ql/exec/ReduceSinkOperator.java