我需要为嵌套搜索创建类型吗？

Question

I see examples like:

var result = this._client.Search(s => s
.Index("my-index")
.Type("my-type")
 .Query(q=> ....)
 .Filter(f=> ....)         
);

But when I use this I get:

The type arguments for method 'Nest.ElasticClient.Search<T>(System.Func<Nest.SearchDescriptor<T>,Nest.SearchDescriptor<T>>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.   

I have lots of different types and I don't want to create classes for all of them. Can I use NEST and it's search without types like Search<MyType> ?

Thanks

Answer 1

I have successfully used Search<dynamic> to avoid needing to be dependent upon a specific type. Then when I get my results back I can examine them and cast/convert into a specific POCO if desired.

I use something like the following:

var result = client.Search<dynamic>(s => s
     .Index("myIndex")
     .AllTypes()
     .Query(q => ...)
     .Filter(f => ...)
);

foreach (var hit in result.Hits.Hits)
{
     //check hit.Type and then map hit.Source into the appropriate POCO.
     // I use AutoMapper for the mapping, but you can do whatever suits you.
     if (string.Compare(hit.Type, "myType", StringCompare.OrdinalIgnoreCase) == 0)
     {
           var myType = AutoMapper.Mapper<MyType>(hit.Source);
     }
}

Answer 2

There is one more solution. NEST 5.x and less uses Newtonsoft.Json for JSON serialization. So you can use JObject instead of dynamic .

var result = client.Search<JObject>(s => s
    .Index("music")
    .AllTypes()
    .Query(q => ...)
    .Filter(f => ...)
);

This is very useful because you can convert it now to any object using Newtonsoft.Json functionality.

private static Dictionary<string, Type> TypeMapping = new Dictionary<string, Type>
{
    { "artist", typeof(Artist) },
    { "song", typeof(Song) }
};

...

foreach (var hit in result.Hits)
{
    var type = TypeMapping[hit.Type];
    var result = hit.Source.ToObject(type);
}

NEST 6.x ships with a shaded Json.NET dependency. So in order to use Newtonsoft.Json for this version you need to install NEST.JsonNetSerializer package and specify JsonNetSerializer.Default .

var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
var connectionSettings =
    new ConnectionSettings(pool, sourceSerializer: JsonNetSerializer.Default);
var client = new ElasticClient(connectionSettings);