ElasticSearch: sorting on strings doesn't support the "missing" option

query_output.txt

// Setup
{"ok":true,"acknowledged":true}
{"ok":true,"acknowledged":true}
{"ok":true,"_index":"test","_type":"tweets","_id":"1","_version":1}
{"ok":true,"_index":"test","_type":"tweets","_id":"2","_version":1}
{"ok":true,"_index":"test","_type":"tweets","_id":"3","_version":1}

// The first query, with the "missing" option, fails.
{
  "error" : "SearchPhaseExecutionException[Failed to execute phase [query], total failure; shardFailures {[Z5lN30goQ0euwj3ce-OPrA][test][1]: SearchParseException[[test][1]: from[-1],size[-1]: Parse Failure [Failed to parse source [\n{ sort : [ { name : {order : \"asc\", missing: \"_last\"} } ] }\n]]]; nested: ElasticSearchIllegalArgumentException[Sorting on string type field does not support missing parameter]; }{[Z5lN30goQ0euwj3ce-OPrA][test][4]: SearchParseException[[test][4]: from[-1],size[-1]: Parse Failure [Failed to parse source [\n{ sort : [ { name : {order : \"asc\", missing: \"_last\"} } ] }\n]]]; nested: ElasticSearchIllegalArgumentException[Sorting on string type field does not support missing parameter]; }{[Z5lN30goQ0euwj3ce-OPrA][test][2]: SearchParseException[[test][2]: from[-1],size[-1]: Parse Failure [Failed to parse source [\n{ sort : [ { name : {order : \"asc\", missing: \"_last\"} } ] }\n]]]; nested: ElasticSearchIllegalArgumentException[Sorting on string type field does not support missing parameter]; }]",
  "status" : 500
}

// The second query, without the "missing" option, works.
{
  "took" : 3,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : null,
    "hits" : [ {
      "_index" : "test",
      "_type" : "tweets",
      "_id" : "2",
      "_score" : null, "_source" : { },
      "sort" : [ null ]
    }, {
      "_index" : "test",
      "_type" : "tweets",
      "_id" : "3",
      "_score" : null, "_source" : { name : "Goldbug" },
      "sort" : [ "goldbug" ]
    }, {
      "_index" : "test",
      "_type" : "tweets",
      "_id" : "1",
      "_score" : null, "_source" : { name : "Grimlock" },
      "sort" : [ "grimlock" ]
    } ]
  }
}

test.sh

curl -X DELETE 'localhost:9200/test'
curl -X PUT 'localhost:9200/test'

curl -X POST 'localhost:9200/test/tweets/1' -d '{ name : "Grimlock" }'
curl -X POST 'localhost:9200/test/tweets/2' -d '{ }'
curl -X POST 'localhost:9200/test/tweets/3' -d '{ name : "Goldbug" }'
sleep 1

curl 'localhost:9200/test/tweets/_search?pretty=true' -d '
{ sort : [ { name : {order : "asc", missing: "_last"} } ] }
'

curl 'localhost:9200/test/tweets/_search?pretty=true' -d '
{ sort : [ { name : {order : "asc"} } ] }
'