I don't want to downplay your work (which can be very helpful, I can see graphs being implemented natively), but why not use EVAL [0] and lua scripts for this ? I instinctively think that performance would be similar but:

- it would be more easily maintainable and extendable (lua scripts vs redis fork)

- it would still be usable in any language (because all you need is EVAL the scripts)

[0] http://redis.io/commands/eval