What useful algorithms do there exist that work on huge data streams and also their results are fairly small and one can compute the result for a mixture of two streams by somehow merging their results?
I can name a few:
- The obvious things like sum, min, max, count, top-K etc.
- Approximate so called "sketch-based" stream algorithms for histograms, counting distinct items or computing quantiles
What others are there?
(I'm interested because I'm writing a hobby project for monitoring distributed systems whose usefulness is directly determined by the usefulness of such algorithms)