Elastic search 2.0 搜索类似查询

Question

This is my model:

[ElasticsearchType(Name = "projectmodel")]
public class ProjectModel
{          
    public string name { get; set; }
    public string description { get; set; }
    [Nested]
    [JsonProperty("taskmodels")]
    public List<TaskModel> taskmodels { get; set; }
}

public class TaskModel
{       
    public string title { get; set; }
    public string description { get; set; }
}

I use the following code for search inside the main object and nested object.

        var searchResults = client.Search<ProjectModel>(
            body => body.Query(
                query => query.Bool(
                    bq => bq.Should(
                        q => q.Match(p => p.Field(f => f.name).Boost(6).Query(keyword)),                            
                        q => q.Match(p => p.Field(f => f.description).Boost(6).Query(keyword)),
                            sh => sh.Nested(n => n.Path(p => p.taskmodels).Query(nq => nq.Match(
                                m => m.Query(keyword).Field("taskmodels.description")

                                )
                            )
                            ),
                            sh => sh.Nested(n => n.Path(p => p.taskmodels).Query(nq => nq.Match(
                                m => m.Query(keyword).Field("taskmodels.title")

                                )
                            )
                            )
                        )

                    )
                ).Size(MAX_RESULT)
            );

This searches the object without any issue. But I need to enter the exact word for searchText to get the result.

As an example: name - "Science and technology"

If I search with technology, It returns the record. But If I search with techno, It did not return the record. How can I fix this issue?

Answer 1

You can add match_phrase_prefix query on on your field.

Match_phrase_prefix will take last token in your searchquery and do a phrase prefix match on it. Order of tokens is important. If you want to search anywhere in the text, then you will need to create n-grams and edge_grams of tokens

var searchResults = _elasticClient.Search<ProjectModel>(
            body => body.Query(
                query => query.Bool(
                    bq => bq.Should(
                        q=> q.MatchPhrasePrefix(p=>p.Field(f=>f.name).Query(keyword)) --> note
                        q => q.Match(p => p.Field(f => f.name).Boost(6).Query(keyword)),
                        q => q.MatchPhrasePrefix(p => p.Field(f => f.description).Boost(6).Query(keyword)),
                            sh => sh.Nested(n => n.Path(p => p.taskmodels).Query(nq => nq.Match(
                                m => m.Query(keyword).Field("taskmodels.description")

                                )
                            )
                            ),
                            sh => sh.Nested(n => n.Path(p => p.taskmodels).Query(nq => nq.Match(
                                m => m.Query(keyword).Field("taskmodels.title")

                                )
                            )
                            )
                        )

                    )
                ).Size(MAX_RESULT)
            );

Different between match, matchphrase and matchphraseprefix

Suppose there is a document with field "description": "science and technology" This text is broken in separate tokens ["science","and","technology"] and stred in inverted index.

If you want to look for "science technology", you can use match query. For match order of words don't matter, so you will also get document when you search for "technology science". It just matches tokens.

If order matters for you then use match_phrase "science and technology" only will return the document.

If you want to search for partial sentence "science and techno" then use match_phrase_prefix. Prefix match is only performed on last token so you cannot search for "scie and techno". For this there are other options like edge-ngrams and ngrams