title: not equal query in elasticsearch
body: <p>I have a field in my index contain a string data.. I run dsl query below expected documents which category fields is not equal to "-" character.. but as you see pic it returns.. 
  What is the way of retrieve these data ? </p>
  
  <pre><code>GET webproxylog/_search
  {
    "query": {
      "filtered": {
        "query": {"match_all": {}},
        "filter": {
          "not": {
            "filter": {
              "term": {
                "category": "-"
              }
            }
          }
        }
      }
    }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/MWqnx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MWqnx.png" alt="enter image description here"></a></p>
  
  <p>mappings:</p>
  
  <pre><code>{
     "webproxylog": {
        "mappings": {
           "accesslog": {
              "properties": {
                 "category": {
                    "type": "string"
                 },
                 "clientip": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "clientmac": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "clientname": {
                    "type": "string"
                 },
                 "duration": {
                    "type": "long"
                 },
                 "filetype": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "hierarchycode": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "loggingdate": {
                    "type": "date",
                    "format": "dateOptionalTime"
                 },
                 "reqmethod": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "respsize": {
                    "type": "long"
                 },
                 "resultcode": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "url": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "user": {
                    "type": "string",
                    "index": "not_analyzed"
                 }
              }
           }
        }
     }
  }
  </code></pre>