Question

Given that I have a Foo model w/ the standard Rails timestamp columns what would be the most efficient way to calculate the average number of days between records being created?

Answer 1

The maximum and minimum class methods of your model will use the SQL aggregate functions min() and max() to find the extreme values efficiently.

span_secs = Foo.maximum(:created_at) - Foo.minimum(:created_at)
avg_secs = span_secs / (Foo.count - 1)
avg_days = avg_secs / (24 * 60 * 60)