private int generateHashSetResults(VectorizedRowBatch batch,
      int[] allMatches, int allMatchCount)
          throws HiveException, IOException {

    int numSel = 0;

    // Generate result within big table batch itself.

    for (int i = 0; i < allMatchCount; i++) {

      int batchIndex = allMatches[i];

      // Use the big table row as output.
      batch.selected[numSel++] = batchIndex;
    }

    return numSel;
  }
Generate the matching left semi join output results of a vectorized row batch.

@param batch
         The big table batch.
@param allMatches
         A subset of the rows of the batch that are matches.
@param allMatchCount
         Number of matches in allMatches.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/mapjoin/VectorMapJoinLeftSemiGenerateResultOperator.java