private static List<String> sequentialStrings(String prefix, int n) {
    List<String> lst = new ArrayList<>();
    for (int i = 0; i < n; ++i) {
      StringBuilder sb = new StringBuilder();
      sb.append(prefix + i);

      // Make column length depend on i.
      int iBitShifted = i;
      while (iBitShifted != 0) {
        sb.append((iBitShifted & 1) == 0 ? 'a' : 'b');
        iBitShifted >>= 1;
      }

      lst.add(sb.toString());
    }
    return lst;
  }
The probability to delete a row/column pair
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMultiColumnScanner.java