public void nullColumn(int columnIndex) {
      eachColumnValueLen[columnIndex] = 0;
      eachColumnUncompressedValueLen[columnIndex] = 0;
      allCellValLenBuffer[columnIndex] = new NonSyncDataOutputBuffer();
    }
KeyBuffer is the key of each record in RCFile. Its on-disk layout is as
below:

<ul>
<li>record length in bytes,it is the sum of bytes used to store the key
part and the value part.</li>
<li>Key length in bytes, it is how many bytes used by the key part.</li>
<li>number_of_rows_in_this_record(vint),</li>
<li>column_1_ondisk_length(vint),</li>
<li>column_1_row_1_value_plain_length,</li>
<li>column_1_row_2_value_plain_length,</li>
<li>....</li>
<li>column_2_ondisk_length(vint),</li>
<li>column_2_row_1_value_plain_length,</li>
<li>column_2_row_2_value_plain_length,</li>
<li>.... .</li>
<li>{the end of the key part}</li>
</ul>
ql/src/java/org/apache/hadoop/hive/ql/io/RCFile.java