@Override
  public void closeOp(boolean aborted) throws HiveException {
    super.closeOp(aborted);
    for (MapJoinTableContainer tableContainer : mapJoinTables) {
      if (tableContainer != null) {
        tableContainer.dumpMetrics();
      }
    }
    if (!aborted) {
      if (outputBatch.size > 0) {
        flushOutput();
      }
    }
  }
'forwards' the (row-mode) record into the (vectorized) output batch
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorMapJoinBaseOperator.java