Unconfigured field _index_preview in server logs

NEST/Elasticsearch.Net version: NEST 7.14.1

Elasticsearch version: 7.14.0

.NET runtime version: net5.0

Operating system version: Windows 10

Description of the problem including expected versus actual behavior: I have a multi field index with a prefixed textfield. In the server logs I see the following message very often:

[WARN ][o.e.i.s.IndexShard       ] no index mapper found for field: [descriptions.prefix._index_prefix] returning default postings format

I don’t see any way to solve this warning.

Steps to reproduce: Execute the following test

[Fact]
public async Task TestRaw()
{
    var indexName = $"{ Guid.NewGuid()}";
    var connectionPool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));

    var connectionSettings = new ConnectionSettings(connectionPool)
        .DefaultMappingFor<ElasticTestIndexEntry>(m => m
            .IndexName(indexName)
        )
        .EnableDebugMode()
        .ThrowExceptions()
        //.DisableDirectStreaming()
        ;

    var client = new ElasticClient(connectionSettings);

    try
    {
        await client.Indices.CreateAsync(indexName, c => c
            .Map<ElasticTestIndexEntry>(m => m
                .AutoMap()
                .Properties(p => p
                    .Text(t => t
                        .Name(n => n.Descriptions)
                        .Fields(f => f
                            .Text(tt => tt
                                .Name("prefix")
                                .IndexPrefixes(pp => pp)
                            )
                        )
                    )
                )
            )
        );

        var bulkEntry = new BulkDescriptor();
        bulkEntry.Refresh(Refresh.WaitFor);
        bulkEntry.Index<ElasticTestIndexEntry>(i => i.Document(new ElasticTestIndexEntry() 
        {
            Descriptions = new List<string>()
            { 
                "abc def",
            },
        }));
        var bulkResponse = await client.BulkAsync(bulkEntry);
        bulkResponse.ItemsWithErrors.Should().BeEmpty();
    }
    finally
    {
        await client.Indices.DeleteAsync(indexName);
    }
}

public class ElasticTestIndexEntry
{
    public List<string> Descriptions { get; set; }
}

Then you have the warning in the server logs.

Expected behavior The nest configuration configures the index correct so that no warning is in the log.

[stevejgordon]

Hi @MartinDemberger. At a first glance, the generated mapping looks okay to me. I’m awaiting some input from colleagues to see if there’s something specific about this case we need to be aware of.

[stevejgordon]

Closing as I believe this has been answered.