title: Elasticsearch no mapping found for sort on field
body: <blockquote>
    <p>No mapping found for field in order to sort on [created_at]</p>
  </blockquote>
  
  <p>What does this message actually means? the field by itself created_at exists, should I rebuild the indexes? or is there a way to fix this <code>error</code>?</p>
  
  <p>UPDATED :</p>
  
  <pre><code>{
     "query":{
        "bool":{
           "must":{
              "multi_match":{
                 "query":"phone",
                 "fields":[
                    "text"
                 ],
                 "minimum_should_match":"100%"
              }
           },
           "filter":{
  
           }
        }
     },
     "sort":[
        {
           "created_at":{
              "order":"desc"
           }
        }
     ]
  }
  </code></pre>