Executing nested aggregation

Nested aggregations allow us to execute analysis on nested documents. When working with complex structures, nested objects are very common.

Getting ready

You need a working ElasticSearch cluster and an index populated with the script available at https://github.com/aparo/elasticsearch-cookbook-second-edition.

How to do it...

To execute nested aggregations, we will perform the steps given as follows:

1. We must index documents with a nested type, as discussed in the Managing nested objects recipe in Chapter 3, Managing Mapping:

   {
     "product" : {
       "properties" : {
         "resellers" : {
           "type" : "nested"
           "properties" : {
             "username" : { "type" : "string", "index" : "not_analyzed" },
             "price" : { "type" : "double" }
           }
         },
         "tags" : { "type" : "string&quot...