$ perl time_to_add_doc.plx
          s/iter   size_4M   size_2M   size_1M size_500k size_250k
size_4M     16.4        --      -51%      -77%      -87%      -94%
size_2M     8.00      105%        --      -53%      -73%      -87%
size_1M     3.73      340%      114%        --      -41%      -72%
size_500k   2.20      646%      264%       70%        --      -52%
size_250k   1.06     1450%      656%      253%      108%        --
$