KNN search on opensearch using .Net

Hello,

To perform knn field search using .Net, you can utilise the "OpenSearch .NET clients". I have provided a sample below:

Firstly I have created an index with the below setting:

PUT my-index
{
  "settings": {
    "index.knn": true
  },
  "mappings": {
    "properties": {
      "my_vector1": {
        "type": "knn_vector",
        "dimension": 2
      },
      "my_vector2": {
        "type": "knn_vector",
        "dimension": 4
      }
    }
  }
}

Then I have ingested some sample data using _bulk request as shown below:

POST _bulk
{ "index": { "_index": "my-index", "_id": "1" } }
{ "my_vector1": [1.5, 2.5], "price": 12.2 }
{ "index": { "_index": "my-index", "_id": "2" } }
{ "my_vector1": [2.5, 3.5], "price": 7.1 }
{ "index": { "_index": "my-index", "_id": "3" } }
{ "my_vector1": [3.5, 4.5], "price": 12.9 }
{ "index": { "_index": "my-index", "_id": "4" } }
{ "my_vector1": [5.5, 6.5], "price": 1.2 }
{ "index": { "_index": "my-index", "_id": "5" } }
{ "my_vector1": [4.5, 5.5], "price": 3.7 }
{ "index": { "_index": "my-index", "_id": "6" } }
{ "my_vector2": [1.5, 5.5, 4.5, 6.4], "price": 10.3 }
{ "index": { "_index": "my-index", "_id": "7" } }
{ "my_vector2": [2.5, 3.5, 5.6, 6.7], "price": 5.5 }
{ "index": { "_index": "my-index", "_id": "8" } }
{ "my_vector2": [4.5, 5.5, 6.7, 3.7], "price": 4.4 }
{ "index": { "_index": "my-index", "_id": "9" } }
{ "my_vector2": [1.5, 5.5, 4.5, 6.4], "price": 8.9 }

After this, I have used the below sample code to perform knn search. Kindly, modify the code based on your requirement:

 
using OpenSearch.Net ;
using OpenSearch.Client;
using OpenSearch.Net .Auth.AwsSigV4;

namespace vs;

class Program
{
    public static void Main(string[] args)
    {
        // Create a client with custom settings
        var uri = new Uri("https://search-xxxx.region.es.amazonaws.com ");
        var connection = new AwsSigV4HttpConnection();
        var settings = new ConnectionSettings(uri, connection);
        var client = new OpenSearchLowLevelClient(settings);

        Console.WriteLine("knn query search sample");

        var searchResponse = client.Search <StringResponse>("my-index",
            @"{
                ""size"": 2,
                ""query"": {
                    ""knn"": {
                        ""my_vector2"": {
                            ""vector"": [2, 3, 5, 6],
                            ""k"": 2
                            }
                        }
                    }
                }");

        Console.WriteLine(searchResponse.Body);
    }
}

Dependencies:

• Opensearch.Net NuGet: https://www.nuget.org/packages/OpenSearch.Net
• OpenSearch.Client NuGet: https://www.nuget.org/packages/OpenSearch.Client/
• OpenSearch.Net.Auth.AwsSigV4 NuGet: https://www.nuget.org/packages/OpenSearch.Net.Auth.AwsSigV4

Reference:

• k-Nearest Neighbor (k-NN) search in Amazon OpenSearch Service - https://docs.aws.amazon.com/opensearch-service/latest/developerguide/knn.html
• OpenSearch .NET clients - https://opensearch.org/docs/latest/clients/dot-net/
• OpenSearch .NET sample program - https://opensearch.org/docs/latest/clients/OpenSearch-dot-net/#sample-program