@Override
    public int getHashFromKey() throws SerDeException {
      if (!(key instanceof BinaryComparable)) {
        throw new SerDeException("Unexpected type " + key.getClass().getCanonicalName());
      }
      sanityCheckKeyForTag();
      BinaryComparable b = (BinaryComparable)key;
      return HashCodeUtil.murmurHash(b.getBytes(), 0, b.getLength() - (hasTag ? 1 : 0));
    }
Get hash value from the key.
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/MapJoinBytesTableContainer.java