Pipeline aggregations, as their name suggests, allow you to aggregate over the result of another aggregation. They let you pipe the result of an aggregation as an input to another aggregation. Pipeline aggregations are a relatively new feature and they are still experimental. At a high level, there are two types of pipeline aggregation:
- Parent pipeline aggregations have the pipeline aggregation nested inside other aggregations
- Sibling pipeline aggregations have the pipeline aggregation as the sibling of the original aggregation from which pipelining is done
Let us understand how the pipeline aggregations work by taking one example of cumulative sum aggregation, which is a parent of pipeline aggregation.