public int getVectorizedKeyDistLength(int batchIndex) {
    return distKeyLengths[batchIndexToResult[batchIndex]];
  }
After vectorized batch is processed, can return distribution keys length of a key.
@param batchIndex index of the key in the batch.
@return The distribution length corresponding to the key.
ql/src/java/org/apache/hadoop/hive/ql/exec/TopNHash.java