Executing terms facets

The terms facet is one of the most used ones. It counts the terms that are in a field of resulting hits. This facet is often used to drill down search.

Getting ready

You need a working ElasticSearch cluster and an index populated with the script available in the online code.

How to do it...

For executing a term facet, we will perform the steps given as follows:

1. We want to calculate the tag count of all the documents: the REST call should be:

   curl -XGET 'http://127.0.0.1:9200/test-index/test-type/_search?pretty=true&size=0' -d '{
       "query": {
           "match_all": {}
       },
       "facets": {
           "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, should be:

   {
     "took" : 2,
     "timed_out" : false,
     "_shards" : {
       "total" : 5,
       "successful" : 5,
     ...