Elasticsearch 2.x allows us to use three types of aggregation: metrics, buckets, and pipeline. The metrics aggregations return a metric, just like the
stats aggregation we used for the
stats field. The bucket aggregations return buckets, the key and the number of documents sharing the same values, ranges, and so on, just like the
terms aggregation we used for the
copies field. Finally, the pipeline aggregations introduced in Elasticsearch 2.0 aggregate the output of the other aggregations and their metrics, which allows us to do even more sophisticated data analysis. Knowing all that, let's now look at all the aggregations we can use in Elasticsearch 2.x.
We will start with the metrics aggregations, which can ...