ElasticSearch & attachment type (NEST C#)

Question

I'm trying to index a pdf document with elasticsearch/NEST.

The file is indexed but search results returns with 0 hits.

I need the search result to return only the document Id and the highlight result

(without the base64 content)

Here is the code:

I'll appreciate any help here,

Thanks,

class Program
{
    static void Main(string[] args)
    {
        // create es client
        string index = "myindex";

        var settings = new ConnectionSettings("localhost", 9200)
            .SetDefaultIndex(index);
        var es = new ElasticClient(settings);

        // delete index if any
        es.DeleteIndex(index);

        // index document
        string path = "test.pdf";
        var doc = new Document()
        {
            Id = 1,
            Title = "test",
            Content = Convert.ToBase64String(File.ReadAllBytes(path))
        };

        var parameters = new IndexParameters() { Refresh = true };
        if (es.Index<Document>(doc, parameters).OK)
        {
            // search in document
            string query = "semantic"; // test.pdf contains the string "semantic"

            var result = es.Search<Document>(s => s
                .Query(q =>
                    q.QueryString(qs => qs
                        .Query(query)
                    )
                )
                .Highlight(h => h
                    .PreTags("<b>")
                    .PostTags("</b>")
                    .OnFields(
                      f => f
                        .OnField(e => e.Content)
                        .PreTags("<em>")
                        .PostTags("</em>")
                    )
                )
            );

            if (result.Hits.Total == 0)
            {
            }
        }
    }
}

[ElasticType(
    Name = "document",
    SearchAnalyzer = "standard",
    IndexAnalyzer = "standard"
)]
public class Document
{
    public int Id { get; set; }

    [ElasticProperty(Store = true)]
    public string Title { get; set; }

    [ElasticProperty(Type = FieldType.attachment,
        TermVector = TermVectorOption.with_positions_offsets)]
    public string Content { get; set; }
}

Answer 1

Install the Attachment Plugin and restart ES

bin/plugin -install elasticsearch/elasticsearch-mapper-attachments/2.3.2

Create an Attachment Class that maps to the Attachment Plugin Documentation

  public class Attachment
  {
      [ElasticProperty(Name = "_content")]
      public string Content { get; set; }

      [ElasticProperty(Name = "_content_type")]
      public string ContentType { get; set; }

      [ElasticProperty(Name = "_name")]
      public string Name { get; set; }
  }

Add a property on the Document class you are indexing with the name "File" and correct mapping

  [ElasticProperty(Type = FieldType.Attachment, TermVector = TermVectorOption.WithPositionsOffsets, Store = true)]
  public Attachment File { get; set; }

Create your index explicitly before you index any instances of your class. If you don't do this, it will use dynamic mapping and ignore your attribute mapping. If you change your mapping in the future, always recreate the index.

  client.CreateIndex("index-name", c => c
     .AddMapping<Document>(m => m.MapFromAttributes())
  );

Index your item

  string path = "test.pdf";

  var attachment = new Attachment();
  attachment.Content = Convert.ToBase64String(File.ReadAllBytes(path));
  attachment.ContentType = "application/pdf";
  attachment.Name = "test.pdf";

  var doc = new Document()
  {
      Id = 1,
      Title = "test",
      File = attachment
  };
  client.Index<Document>(item);

Search on the File property

  var query = Query<Document>.Term("file", "searchTerm");

  var searchResults = client.Search<Document>(s => s
          .From(start)
          .Size(count)
          .Query(query)
  );