byte[][] columnRandom;
BytesRefArrayWritable bytes = new BytesRefArrayWritable(columnNum);
columnRandom = new byte[columnNum][];
for (int i = 0; i < columnNum; i++) {
BytesRefWritable cu = new BytesRefWritable();
bytes.set(i, cu);
}
for (int i = 0; i < rowCount; i++) {
nextRandomRow(columnRandom, bytes);