Generalize Store interface

[Sytten]

The first step in implementing a sparse store is making sure we have a Store interface that is agnostic of the underlining implementation. Basically we need to support merging stores using bins.

[Sytten]

First part is done. we now have an iterator on the bins.

[ccollie]

Is it possible to "subtract" one sketch from another ? The use-case is calculating quantiles over a rolling window. Let's say i have a circular list of n sketches which track a metric over a window of size t. After each (t/n) ticks we subtract the current slice from the accumulator.

[Sytten]

Not with the current implementation, I guess you would need an array of sketches because we don't track the values once they are in the bins. And then on each t/n you have to compute a master sketche that combines the bins of all the underlining sketches.

[ccollie]

That would work, though subtraction would be the most performant way to handle it.
Thanks, I'll give it a shot.