protected final void defaultEndGroup() throws HiveException {
    LOG.trace("Ending group");

    if (CollectionUtils.isEmpty(childOperators)) {
      LOG.trace("No children operators; end group done");
      return;
    }

    LOG.trace("Ending group for children");
    for (Operator<? extends OperatorDesc> op : childOperators) {
      op.endGroup();
    }
    LOG.trace("End group done");
  }
Process the row.

@param row
         The object representing the row.
@param tag
         The tag of the row usually means which parent this row comes from.
         Rows with the same tag should have exactly the same rowInspector
         all the time.
ql/src/java/org/apache/hadoop/hive/ql/exec/Operator.java