public void cleanupPartition() {
    blocks.clear();
    for (VectorizedRowBatch batch : bufferedBatches) {
      batch.reset();
    }
    currentBufferedBatchCount = 0;

    resetEvaluators();

    if (boundaryCache != null) {
      boundaryCache.clear();
    }
    if (valueCache != null) {
      valueCache.clear();
    }
    cachedSize = -1;
    partitionMetrics.clear();
  }
This should be called, when all of the batches were processed for a group (all of the
evaluators have been evaluated for this group). The data is not needed anymore.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFGroupBatches.java