Getting order of Entity based on index and property.

[Oliver Billing]

I have a 100.000 entities  and I want the  position of a single Entity compared to the rest, based upon a single property called "score".  I have the Entity's key.

Is this possible without having to iterate through 100.000 entities, for instance using the generated idx on the "score" property.

[alex]

Looks like a perfect task for mapreduce.

[Oliver Billing]

Yeah, but it is too slow and would cost too many read operations *sigh*  Besides the score will be updated frquently

[alex]

If there's nothing else besides that the score will be updated frequently that you forgot to mention, you could still pre-compute initial position using mapreduce and then do partial updates just on the entities that have the score changed. There are a few known algorithms.