基于Elasticsearch进行地理检索，计算距离值

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实现步骤：

1、定义属性

    [Serializable]

    public class Coordinate

    {

        public double Lat { get; set; }

        public double Lon { get; set; }

    }

        /// <summary>

        /// 位置坐标

        /// </summary>

        [ElasticProperty(Type = FieldType.GeoPoint)]

        public Coordinate location { get; set; }

        /// <summary>

        /// 返回字段，距离值，适用于地理位置检索和排序  2016-03-25

        /// </summary>

        public double distance { get; set; }

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2、创建索引时，设置Mapping：

_clientES.CreateIndex(indexName, s => s.AddMapping<DTOCarInfoIndexField>(f => f.MapFromAttributes().Properties(p => p.GeoPoint(g => g.Name(n => n.location).IndexLatLon()).String(fullinfo => fullinfo.Name(n => n.fullinfo).Index(FieldIndexOption.Analyzed).Analyzer("ik").Store(false)).String(description => description.Name(n => n.statedescription).Index(FieldIndexOption.Analyzed).Analyzer("ik").Store(false))).AllField(af => af.Enabled(false))).NumberOfReplicas(0));

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3、向ES写入数据时，给location属性赋值：

#region 车源坐标  2015-11-30

string[] arrValue = ConvertHelper.ToStringArray(value.ToString(), ',');

if (arrValue.Length == 2)

{

    var point = new Coordinate();

    point.Lat = 0.0;

    point.Lon = 0.0;

    double x = ConvertHelper.ToDouble(arrValue[0]);

    double y = ConvertHelper.ToDouble(arrValue[1]);

    if (x > 0 && y > 0)

    {

        point.Lat = x;

        point.Lon = y;

    }

    prop.SetValue(obj, point, null);

}

#endregion

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4、搜索过程中按照距离排序并返回距离值（单位：km）（Nest组件）：

//构建排序对象

List<KeyValuePair<PropertyPathMarker, ISort>> oneSortList = new List<KeyValuePair<PropertyPathMarker, ISort>>();

SortOrder ordertype = SortOrder.Ascending;

GeoDistanceSort sort = new GeoDistanceSort();

sort.Field = "location";

sort.Order = ordertype;

sort.GeoUnit = GeoUnit.Kilometers;

sort.PinLocation = locationpoint;

oneSortList.Add(new KeyValuePair<PropertyPathMarker, ISort>("_geo_distance", sort));

//构建ES检索对象

string[] returnFields=new[]{"id","distance"};

var searchRequest = new SearchRequest();

searchRequest.From = 0;

searchRequest.Size = 20;

searchRequest.Sort = oneSortList;

//定义返回列属性

searchRequest.Fields = returnFields.Select(f => (PropertyPathMarker)f.ToLower()).ToList();

//添加其他检索条件

//searchRequest.Query = queryList[i];

//searchRequest.Filter = listFilter[i];

#region 地理检索，添加距离返回值字段

if (!string.IsNullOrEmpty(locationPoint) && returnFields.Contains("distance"))

{

    var distancefield = new Dictionary<string, IScriptFilter>();

    var tempfield = new ScriptFilter();

    tempfield.Params = new Dictionary<string, object>();

    tempfield.Params.Add("lat", 116.403951);

    tempfield.Params.Add("lon", 39.915031);

    tempfield.Script = "doc['location'].arcDistanceInKm(lat,lon)";

    distancefield.Add("distance", tempfield);

    searchRequest.ScriptFields = distancefield;

}

#endregion

//执行检索，获取返回值

var resultSearch = esClient.Search<T>(searchRequest);

foreach (var doc in sResponse.FieldSelections)

{

    var id = doc.FieldValues<object[]>("id").ToList()[0];

    var distancevalue = doc.FieldValues<object[]>("distance").ToList()[0]; 

}

5、搜索过程中按照距离排序并返回距离值（单位：km）（Linq方式）

ESClient.Instance_TaocheCar().GetElasticClient().Search<DTOCarInfoIndexField>(s => s.From(0).Size(200).Fields(arrField).Filter(filter => filter.Terms("userid", list)).ScriptFields(sf => sf.Add("distance", descriptor => descriptor.Params(p => p.Add("lat", lat).Add("lon", lon)).Script("doc['location'].arcDistanceInKm(lat,lon)"))).SortGeoDistance(sg => sg.OnField("location").PinTo(lat, lon).Unit(GeoUnit.Kilometers).Ascending()));