One CPU cycle per row saves 27 seconds of one CPU's time. That 10 seconds was saved on every CPU in the cluster. So if there were 50 CPUs, that's 500 seconds, o

One CPU cycle per row saves 27 seconds of one CPU's time. That 10 seconds was saved on every CPU in the cluster. So if there were 50 CPUs, that's 500 seconds, or ~20 cycles per record, by the original calculation. In reality, the change in data type probably optimized disk access more than it did number of CPU cycles. That can often be more of a bottleneck.