Executing facets

ElasticSearch provides several functionalities other than search; it allows executing statistics and real-time analytics on searches via the facets.

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 facet, we will perform the steps given as follows:

1. From command line:

    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 case we have used a match_all query plus a term facets used to count terms.

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

   {
     "took" : 2,
     "timed_out" : false,
     "_shards" : {
       "total" : 5,
       "successful" : 5,
       "failed" : 0
     },
     "hits" : {
       "total" : 3,
       "max_score" : 1.0,
       "hits" : [ ]
     },
     "facets" : {
       "tag" :...