error in intervals.union_overlapping

[Charles G Waldman]

The function "union_overlapping" in intervals.py only works if the list of intervals is passed in in sorted order.
However, the ceres backend keeps the slice info in reverse sorted order:
  ceres.py:251 slice_info.sort(reverse=True)

which causes errors accessing Ceres data - measure_of_added_coverage in storage.py returns erroneous results, because it operates on IntervalSets which are invalid.

the attached patch makes the code more robust: it will work regardless of whether the list of intervals is sorted in forward or reverse direction, it is also more readable since it uses the 'overlaps' and 'union' methods of class Interval, rather than comparing start and end times (which is order-dependent)

[Michael Leinartas (mleinartas)]

Thanks, this is a great catch. I've merged this in master: https://github.com/graphite-project/graphite-web/commit/df01d98f090c2cd0c28876f3a409c4f0f0e1a92f

One question - I'm curious, what branch are you running for carbon to work with Ceres?