elasticsearch: get only the elements that has a certain non-empty key from the url

Question

I'de like to filter the results of an elasticsearch query and retrieve only those that have a non-empty field

For example. giving the following data

{
  total: 4912,
  max_score: 1,
  hits: [
{
  {
    _index: "gcba",
    _type: "bafici",
    _id: "5a93472b-5db4-4ff9-8c8a-d13158e72d5f-62",
    _score: 1,
    _source: {
      id_film: "23",
      title: "great film",
    }
  },
  {
    _index: "gcba",
    _type: "bafici",
    _id: "2732fbf4-4e55-4794-8e98-e5d5fa6a0419-40",
    _score: 1,
    _source: {
      name: "conference",
      [...]
    }
  }
}

I'd like to issue something like

.../_search?from=1&size=100&q=id_film:'*'

to get only those elements with an id_film value

Answer 1

ES will only return documents that have that particular field by default when doing a wildcard query:

% curl -XPUT http://localhost:9200/foo/bar/1 -d '{"id":1,"id_film":23}'
{"ok":true,"_index":"foo","_type":"bar","_id":"1","_version":1}%

% curl -XPUT http://localhost:9200/foo/bar/2 -d '{"id":2,"foo":23}'
{"ok":true,"_index":"foo","_type":"bar","_id":"2","_version":1}%

% curl "http://localhost:9200/foo/_search?q=id_film:*&pretty=true"
{
  "took" : 2,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 1.0,
    "hits" : [ {
      "_index" : "foo",
      "_type" : "bar",
      "_id" : "1",
      "_score" : 1.0, "_source" : {"id":1,"id_film":23}
    } ]
  }
}%