Using the top_children query

In the previous recipe, the has_child query consumes a large amount of memory because it requires to fetch IDs of all the children. To bypass this limitation in huge data contexts the top_children query allows fetching only the top children results.

Getting ready

You need a working ElasticSearch cluster and the data populated with the populate script.

How to do it...

For executing the top_children query, we need to perform the following steps:

1. We need to search the test-type parents of which the test-type2 top children have a term in the field value as value1. We can create this kind of query as follows:

   curl -XPOST 'http://127.0.0.1:9200/test-index/test-type/_search' -d '{
       "query": {
               "top_children" : {
                   "type" : "test-type2",
                   "query" : {
                       "term" : {
                           "value" : "value1"
                       }
                   },
                   "score" : "max",
                   "factor" : 5,
       ...