protected org.apache.hadoop.mapred.RecordReader setReaderAtSplit(int splitNum)
      throws IOException {
    JobConf localJc = getLocalFSJobConfClone(jc);
    currentSplitPointer = splitNum;
    if ( rr != null ) {
      rr.close();
    }
    // open record reader to read next split
    rr = inputFormat.getRecordReader(inputSplits[currentSplitPointer], jobCloneUsingLocalFs,
        reporter);
    currentSplitPointer++;
    return rr;
  }
Remove all elements in the RowContainer.
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/RowContainer.java