Executing the terms aggregation

Terms aggregation is one of the most commonly used aggregations. It groups documents in buckets based on a single term value. This aggregation is often used to narrow down a search.

Getting ready

You need a working ElasticSearch cluster and an index populated with the script (chapter_06/executing_terms_aggregation.sh) available at https://github.com/aparo/elasticsearch-cookbook-second-edition.

How to do it...

To execute a terms aggregation, we will perform the steps given as follows:

1. We want to calculate the top-10 tags of all the documents; for this the REST call should be as follows:

   curl -XGET 'http://127.0.0.1:9200/test-index/test-type/_search?pretty=true&size=0' -d '{
     "query": {
       "match_all": {}
     },
     "aggs": {
       "tag": {
         "terms": {
           "field": "tag",
           "size": 10
         }
       }
     }
   }'
   

   In this example, we need to match all the items, so the match_all query is used.

2. The result returned by ElasticSearch, if everything is all right...