@Override
  void run() throws Exception {
    startAbortChecks();
    while (sources[position].pushRecord()) {
      addRowAndMaybeCheckAbort();
    }
  }
Process input from tez LogicalInput and write output - for a map plan
Just pump the records through the query plan.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/MapRecordProcessor.java