我有一些文档的映射，并且查询agains条件确实失败。我不明白为什么：

"mappings":{
     "timeslot":{
            "properties":{
                 "FOB_IN":{
                        "type":"long"
                 },
                 "TRIGGER_CODE":{
                        "type":"long"
                 },
                 "FLIGHT_PHASE":{
                        "type":"long"
                 },
                 "REP16_TRIG":{
                        "type":"long"
                 },
                 "fwot":{
                        "type":"string"
                 },
                 "FOB_OUT":{
                        "type":"long"
                 },
                 "FP":{
                        "type":"long"
                 },
                 "FLTNB":{
                        "type":"string"
                 },
                 "Date":{
                        "format":"strict_date_optional_time||epoch_millis",
                        "type":"date"
                 }
            }
     }
}

TRIGGER_CODE例如，我可以对进行词条查询，效果很好

{
   "took": 1,
   "timed_out": false,
   "_shards": {
      "total": 1,
      "successful": 1,
      "failed": 0
   },
   "hits": {
      "total": 5,
      "max_score": 4.4446826,
      "hits": [
         {
            "_index": "merged-2016-04",
            "_type": "timeslot",
            "_id": "AVRS8VnirVLwfvMnwpXb",
            "_score": 4.4446826,
            "_source": {
               "Date": "2016-04-03T08:42:44+0000",
               "FLIGHT_PHASE": 20,
               "TRIGGER_CODE": 4000,
               "fwot": "A6-APA"
            }
         }
      ]
   }
}

现在 对fwot同样失败 。怎么了？

GET merged-2016-04/_search?size=1
{
    "query" : {
        "term" : { "fwot": "A6-APA"}
    }
}

{
   "took": 1,
   "timed_out": false,
   "_shards": {
      "total": 1,
      "successful": 1,
      "failed": 0
   },
   "hits": {
      "total": 0,
      "max_score": null,
      "hits": []
   }
}