Returning the timestamp field in elasticsearch

Question

Why can I not see the _timestamp field while being able to filter a query by it?

The following query return the correct documents, but not the timestamp itself. How can I return the timestamp?

{
  "fields": [
    "_timestamp",
    "_source"
  ],
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      },
      "filter": {
        "range": {
          "_timestamp": {
            "from": "2013-01-01"
          }
        }
      }
    }
  }
}

The mapping is:

{
    "my_doctype": {
        "_timestamp": {
            "enabled": "true"
        },
        "properties": {
            "cards": {
                "type": "integer"
            }
        }
    }
}

sample output:

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "hits" : {
    "total" : 2,
    "max_score" : 1.0,
    "hits" : [ {
      "_index" : "test1",
      "_type" : "doctype1",
      "_id" : "HjfryYQEQL6RkEX3VOiBHQ",
      "_score" : 1.0, "_source" : {"cards": "5"}
    }, {
      "_index" : "test1",
      "_type" : "doctype1",
      "_id" : "sDyHcT1BTMatjmUS0NSoEg",
      "_score" : 1.0, "_source" : {"cards": "2"}
    }]
  }

Answer 1

It is not necessary to store the timestamp field, since its exact value is preserved as a term, which is also more likely to already be present in RAM, especially if you are querying on it. You can access the timestamp via its term using a script_value:

{
    "query": {
        ...
    },
    "script_fields": {
        "timestamp": {
            "script": "_doc['_timestamp'].value"
        }
    }
}

The resulting value is expressed in miliseconds since UNIX epoch. It's quite obscene that ElasticSearch can't do this for you, but hey, nothing's perfect.