title: How to verify index_name works in elasticsearch
body: <p>How can you verify if index_name property works correctly in elasticsearch. i.e. how to verify if elasticsearch internally stores field key using index_name.</p>
  
  <p>Below is my mapping.</p>
  
  <pre><code>POST testalias
  {
     "mappings": {
        "test": {
           "properties": {
              "keywords" : { "type" : "string", "index_name": "kd" }
           }
        }
     }
  }
  </code></pre>
  
  <p>I store data as below</p>
  
  <pre><code>POST testalias/test/
  {
      "keywords": "mykey123"
  }
  </code></pre>
  
  <p>When I lookup <a href="http://localhost:9200/testalias/_search?q=" rel="nofollow noreferrer">http://localhost:9200/testalias/_search?q=</a>*&amp;pretty I get the response with </p>
  
  <pre><code>"_source":{
      "keywords": "mykey123"
  }
  </code></pre>
  
  <p>So the response shows the field name "keywords", but how can I confirm internally es stores it as "kd". This is important because my field names are very long and I want to use index_name to save disk space. My business reason is based on this post <a href="https://stackoverflow.com/questions/28492785/cost-of-keys-in-json-document-database-mongodb-elasticsearch">cost of keys in JSON document database (mongodb, elasticsearch)</a> </p>