@Override
  public OperatorType getType() {
    return OperatorType.LATERALVIEWJOIN;
  }
An important assumption for processOp() is that for a given row from the
TS, the LVJ will first get the row from the left select operator, followed
by all the corresponding rows from the UDTF operator. And so on.
ql/src/java/org/apache/hadoop/hive/ql/exec/LateralViewJoinOperator.java