Elastic search query with Nest, search for text, but also filtering by flags

Question

I have the following query:

return Q
    .MultiMatch(Fu => Fu
        .Fields(F => F
            .Field(Ff => Ff.Tags)
            .Field(Ff => Ff.Title)
        )
        .Query(Terms)
        .Fuzziness(Fuzziness.EditDistance(2))
    );

How can I add a secondary part to the query that would perform:

"If the document has NO 'score' field OR if 'score' <= 1"

I don't see how to add this part with the API.

Answer 1

Assuming a POCO something like

public class MyDocument 
{
    public string[] Tags { get; set; }

    public string Title { get; set; }

    public int Score { get; set; }
}

You can use the overloaded operators on queries to construct compound bool queries, to satisfy the requirements

var client = new ElasticClient(settings);

var terms = "foo bar baz";

var searchResponse = client.Search<MyDocument>(s => s
    .Query(q => q
        .MultiMatch(mm => mm
            .Fields(f => f
                .Field(ff => ff.Tags)
                .Field(ff => ff.Title)
            )
            .Query(terms)
            .Fuzziness(Fuzziness.EditDistance(2))
        ) && +(!q
        .Exists(e => e
            .Field(f => f.Score)
        ) || q
        .Range(r => r
            .Field(f => f.Score)
            .LessThan(1)
        ))
    )
); 

which results in the query

{
  "query": {
    "bool": {
      "must": [
        {
          "multi_match": {
            "query": "foo bar baz",
            "fuzziness": 2,
            "fields": [
              "tags",
              "title"
            ]
          }
        }
      ],
      "filter": [
        {
          "bool": {
            "should": [
              {
                "bool": {
                  "must_not": [
                    {
                      "exists": {
                        "field": "score"
                      }
                    }
                  ]
                }
              },
              {
                "range": {
                  "score": {
                    "lt": 1.0
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}

This is the more succinct form of the query

var searchResponse = client.Search<MyDocument>(s => s
    .Query(q => q
        .Bool(b => b
            .Must(mu => mu
                .MultiMatch(mm => mm
                    .Fields(f => f
                        .Field(ff => ff.Tags)
                        .Field(ff => ff.Title)
                    )
                    .Query(terms)
                    .Fuzziness(Fuzziness.EditDistance(2))
                )
            )
            .Filter(fi => fi
                .Bool(bb => bb
                    .Should(sh => sh
                        .Bool(bbb => bbb
                            .MustNot(mn => mn
                                .Exists(e => e
                                    .Field(f => f.Score)
                                )
                            )
                        ), sh => sh
                        .Range(r => r
                            .Field(f => f.Score)
                            .LessThan(1)
                        )
                    )
                )
            )
        )
    )
);