Nest SuggestCompletion usage, throws 'is not a completion suggest field' exception

Question

I'm a complete beginner to elasticsearch and I have been trying to use elasticsearch's completion suggester using Nest for auto-complete on a property.

Here is my mapping (as mentioned here: ):

var createResult = client.CreateIndex(indexName, index => index                
            .AddMapping<Contact>(tmd => tmd
                .Properties(props => props
                    .Completion(s =>
                        s.Name(p => p.CompanyName.Suffix("completion"))
                        .IndexAnalyzer("standard")
                        .SearchAnalyzer("standard")
                        .MaxInputLength(20)
                        .Payloads()
                        .PreservePositionIncrements()
                        .PreserveSeparators())                        
                )
            )
        );

var resultPerson = client.IndexMany(documents.OfType<Person>(), new SimpleBulkParameters { Refresh = true });
var resultCompany = client.IndexMany(documents.OfType<Company>(), new SimpleBulkParameters { Refresh = true });

And while indexing I'm just making use of IndexMany method and passing the IEnumerable<Contact> (Contact has a property by name CompanyName, Contact is an abstract class, both Person and Company are concrete implementations of it). The search throws an exception saying

ElasticSearchException[Field [companyName] is not a completion suggest field]

And the query looks like below:

SearchDescriptor<Contact> descriptor = new SearchDescriptor<Contact>();
descriptor = descriptor.SuggestCompletion("suggest", c => c.OnField(f => f.CompanyName).Text(q));

var result = getElasticClientInstance("contacts").Search<Contact>(body => descriptor);

string qe = result.ConnectionStatus.ToString();

What am I doing wrong here, I looked into Nest's tests on SuggestCompletion but not much help, meaning the test only depict on how to get suggestions but not on how to set index mappings for SuggestCompletion.

I also tried setting up edgeNgram tokenizer as mentioned in this post but, couldn't proceed there as well.

Any direction or an example on how to proceed would greatly help.

Answer 1

UPDATE

You are try to create a property with the name "companyName.completion" but at that position its not valid and it will use the last token "completion". So its actually mapping a field called completion.... try changing the call to: .Name(p => p.CompanyName)

Other observations

You specify a mapping for the Contact but while indexing you use the Person and Company types.

In elasticsearch terms you mapped:

/index/contact/

but your documents are going into:

/index/person/ and /index/company

NEST won't automatically map all implementation of a specific class and elasticsearch has no way of knowing the three are related.

I would refactor the mapping to a method and call it for all the types involved.

 var createResult = client.CreateIndex(indexName, index => index                
      .AddMapping<Contact>(tmd => MapContactCompletionFields(tmd))
      .AddMapping<Person>(tmd => MapContactCompletionFields(tmd))
      .AddMapping<Company>(tmd => MapContactCompletionFields(tmd))   
  );

 private RootObjectMappingDescriptor<TContact>  MapContactCompletionFields<TContact>(
      RootObjectMappingDescriptor<TContact> tmd)
      where TContact : Contact
 {
      return  tmd.Properties(props => props
           .Completion(s => s
                .Name(p => p.CompanyName.Suffix("completion"))
                .IndexAnalyzer("standard")
                .SearchAnalyzer("standard")
                .MaxInputLength(20)
                .Payloads()
                .PreservePositionIncrements()
                .PreserveSeparators()
           )                        
       );
 } 

That method returns the descriptor so you can further chain on it.

Then when you do a search for contacts:

var result = getElasticClientInstance("contacts").Search<Contact>(
    body => descriptor
        .Types(typeof(Person), typeof(Company))
);

That types hint will cause the search to looking /index/person and /index/company and will know how to give you back a covariant list of documents.

So you can do result.Documents.OfType<Person>() after the previous call.