The core value of Elasticsearch is to run queries and analytics on top of it. All these in real time make Elasticsearch a unique and widely used combination. Here, real time refers to the ability of Elasticsearch to ingest documents one at a time and to make the document searchable immediately once it's given for indexing. Elasticsearch has a wide range of analytic features as its innate support. From day one, it was built in such a way that all these features could be rendered in real time. It has to also be noted that the scope of aggregation is its query score. This means that the input of the aggregation is the output of the query. The documents matching the query are passed through the aggregation to get the aggregation result.
The highlights of this chapter are as follows:
Nested aggregations can be used to club various aggregations, such as terms, geo, date histogram, and so on, to solve analytics requirements in many cases. This core feature, once mastered properly, can be...