title: How to exclude a field from getting searched by elasticsearch 6.1?
body: <p>I have an index with multiple fields in it. I want to filter out based on presence of search string in all the fields except one - <strong>user_comments</strong>.
  The query search that I am doing is</p>
  
  <pre><code>{
      "from": offset,
      "size": limit,
      "_source": [
        "document_title"
      ],
      "query": {
        "function_score": {
          "query": {
            "bool": {
              "must":
              {
                "query_string": {
                  "query": "#{query}"
                }
              }
            }
          }
        }
      }
    }
  </code></pre>
  
  <p>Although the query string is searching through all the fields, and giving me documents with matching string in the <strong>user_comments</strong> field as well. But, I want to query it against all the fields leaving out the <strong>user_comments</strong> field.
   The white-list is a very big list and also the name of the fields are dynamic, so it is not feasible to mention the white-listed field list using the fields parameter like.</p>
  
  <pre><code>"query_string": {
                      "query": "#{query}",
                      "fields": [
                        "document_title",
                        "field2"
                      ]
                    }
  </code></pre>
  
  <p>Can anybody please suggest an idea on how to exclude a field from being searched?</p>