private boolean pushRecordVector() {
    try {
      if (!reader.next()) {
        return false;
      }

      BytesWritable keyWritable = (BytesWritable) reader.getCurrentKey();
      valueWritables = reader.getCurrentValues();

      processVectorGroup(keyWritable, valueWritables, tag);
      return true;
    } catch (Throwable e) {
      abort = true;
      if (e instanceof OutOfMemoryError) {
        // Don't create a new object if we are already out of memory
        throw (OutOfMemoryError) e;
      } else {
        l4j.error(StringUtils.stringifyException(e));
        throw new RuntimeException(e);
      }
    }
  }
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/ReduceRecordSource.java