Elasticsearch Range filter with year only

I need to filter my data with year only using elastic search. I am using PHP to fetch and show the results. Here is my JSON Format data

 {    loc_cityname: "New York",
    location_countryname: "US",
    location_primary: "North America"
    admitted_date  : "1994-12-10"
 },
     {    loc_cityname: "New York",
    location_countryname: "US",
    location_primary: "North America"
    admitted_date  : "1995-12-10"
 },

I am using below codes to filter the values by year.

$options='{
    "query": {
        "range" : {
            "admitted_date" : {
                "gte" : 1994,
                "lte" : 2000
            }
        }
    }, 
    "aggs" : {
    "citycount" : {
        "cardinality" : {
            "field" : "loc_cityname",
            "precision_threshold": 100
    }
   }
  }
}';

How can i filter the results with year only. Please somebody help me to fix this.

Thanks in advance,

You simply need to add the format parameter to your range query like this:

$options='{
    "query": {
        "range" : {
            "admitted_date" : {
                "gte" : 1994,
                "lte" : 2000,
                "format": "yyyy"         <--- add this line
            }
        }
    }, 
    "aggs" : {
    "citycount" : {
        "cardinality" : {
            "field" : "loc_cityname",
            "precision_threshold": 100
    }
   }
  }
}';

UPDATE Note that the above solution only works for ES 1.5 and above. With previous versions of ES, you could use a script filter instead:

$options='{
  "query": {
    "filtered": {
      "filter": {
        "script": {
          "script": "(min..max).contains(doc.admitted_date.date.year)",
          "params": {
            "min": 1994,
            "max": 2000
          }
        }
      }
    }
  },
  "aggs": {
    "citycount": {
      "cardinality": {
        "field": "loc_cityname",
        "precision_threshold": 100
      }
    }
  }
}';

In order to be able to run this script filter, you need to make sure that you have enabled scripting in elasticsearch.yml:

script.disable_dynamic: false