The 95 percentile for query response times is and old
concept; Peter and Roland blogged about it in 2008. Since then,
MySQL tools have calculated the 95 percentile by collecting all
values, either exactly or approximately, and returning
all_values[int(number_of_values * 0.95)] (that’s an
extreme simplification). But recently I asked myself*: must we
save all values? The answer is no. I created a new algorithm**
for calculating the 95 percentile that is faster, more accurate,
and saves only 100 values.***
Firstly, my basis of comparison is the 95 percentile algo used by …
[Read more]