@Override
      protected void map(ImmutableBytesWritable key, Result value, Context context)
        throws IOException, InterruptedException {
        byte[] rowKey = key.get();
        row.set(rowKey, 0, rowKey.length);
        if (
          multipleUnevenColumnFamilies && (!value.containsColumn(BIG_FAMILY_NAME, BIG_FAMILY_NAME)
            || !value.containsColumn(TINY_FAMILY_NAME, TINY_FAMILY_NAME))
        ) {
          context.write(row, DEF_LOST_FAMILIES);
        } else {
          context.write(row, DEF);
        }
        byte[] prev = value.getValue(FAMILY_NAME, COLUMN_PREV);
        if (prev != null && prev.length > 0) {
          ref.set(prev, 0, prev.length);
          context.write(ref, row);
        } else {
          LOG.warn(String.format("Prev is not set for: %s", Bytes.toStringBinary(rowKey)));
        }
      }
A Map Reduce job that verifies that the linked lists generated by {@link Generator} do not have
any holes.
hbase-it/src/test/java/org/apache/hadoop/hbase/test/IntegrationTestBigLinkedList.java