How to get Elasticsearch score result detail?

Question

I have an elastic index that keeps some items. The structure is below.

public class items
{
    public string item_no { get; set; }
    public string category { get; set; }
    public int campaign { get; set; }
    public int in_stock { get; set; }
    // Next properties only include [a-z0-9]. Not any other characters
    public string score_item_no { get; set; }   
    public string score_group_one { get; set; }
    public string score_group_two { get; set; }
    public string score_description { get; set; }
    public string score_all_fields { get; set; } /* score_item_no + score_group_one + score_group_two + score_description and something else */
}

public class ClassForScore
{
        public int id { get; set; }
        public string item_no { get; set; }
}

I must filter useless records from the result. I've decided to use the score option and made a function to calculate the average score. So first I call the elasticsearch for scores, and then I call with minscore parameter. I could not find any solution for filtering useless resultsAny advice for this? This is question one.

And the second one: The first score call returns 7 records. Every record has different scores. For example, the first record has 1100 scores. But I would like to know where this 1100 comes from? 1000 from score_item_no and 100 from score_group_one, or 500 from score_group_one matching 5 parts and 500 of them score_group_two match 5 parts and 100 from score_description matching 2 parts. Is there a way to find score detail?

    QueryContainer queryContainsAnd = new WildcardQuery() { Field = "score_all_fields", Value = "*" + mykeyword + "*" };
    QueryContainer queryEqualsOr =  new TermQuery() { Field = "category", Value = *something1* };
    queryEqualsOr |=  new TermQuery() { Field = "category", Value = *something2* };
    QueryContainer queryEqualsAnd = new TermQuery() { Field = "campaign", Value = 1 };
    queryEqualsAnd &= new TermQuery() { Field = "in_stock", Value = 1 };
            
            
    QueryContainer mainQuery = queryContainsAnd & queryEqualsAnd & queryEqualsOr;
    
    Func<QueryContainerDescriptor<ClassForScore>, QueryContainer> fo = funcScoreParam(new ClassForScore(), filterItemNo, filterGroupOne, filterGroupTwo, filterDescription, mainQuery);
    ISearchResponse<ClassForScore> srcSkor = elasticClient.Search<ClassForScore>(s => s
        .RequestConfiguration(r => r.DisableDirectStreaming())
        .Query(fo)
        .Size(100)
    );
    IReadOnlyCollection<IHit<ClassForScore>> lstSkor = srcSkor.Hits;
    double? dblSkorAvg = 0;
    // Some calculation..
    //.....
    Func<QueryContainerDescriptor<items>, QueryContainer> fo2 = funcScoreParam(new ClassForScore(), filterItemNo, filterGroupOne, filterGroupTwo, filterDescription, mainQuery);
    ISearchResponse<items> srcResult = elasticClient.Search<items>(s => s
        .RequestConfiguration(r => r.DisableDirectStreaming())
        .From(0)
        .Size(100)
        .Sort(S => S.Descending(SortSpecialField.Score).Ascending(r => r.item_no))
        .MinScore(dblSkorAvg)
        .Query(fo2)
    );
    
    
    private Func<QueryContainerDescriptor<T>, QueryContainer> funcScoreParam<T>(T nesne, QueryContainer filterItemNo, QueryContainer filterGroupOne, QueryContainer filterGroupTwo, QueryContainer filterDescription, QueryContainer mainQuery) where T : class
    {
        return new Func<QueryContainerDescriptor<T>, QueryContainer>(q => q
            .FunctionScore(fsc => fsc
                .BoostMode(FunctionBoostMode.Sum)
                .ScoreMode(FunctionScoreMode.Sum)
                .Functions(fu => fu
                        .Weight(w => w
                            .Weight(1000)
                            .Filter(wf => wf
                            .Bool(bb => bb
                            .Must(filterItemNo))
                            ))
                        .Weight(w => w
                            .Weight(100)
                            .Filter(wf => wf
                            .Bool(bb => bb
                            .Must(filterGroupOne))
                            ))
                        .Weight(w => w
                            .Weight(100)
                            .Filter(wf => wf
                            .Bool(bb => bb
                            .Must(filterGroupTwo)) 
                            ))
                        .Weight(w => w
                            .Weight(50)
                            .Filter(wf => wf
                            .Bool(bb => bb
                            .Must(filterDescription))
                            ))
                    )
                    .Query(q2 => q2
                        .Bool(b => b
                        .Should(mainQuery))
                    )
        ));
    }

Answer 1

You can use the explain parameter on the search API to return detailed information about score computation for each hit

ISearchResponse<items> srcResult = elasticClient.Search<items>(s => s
    .RequestConfiguration(r => r.DisableDirectStreaming())
    .From(0)
    .Size(100)
    .Sort(S => S.Descending(SortSpecialField.Score).Ascending(r => r.item_no))
    .MinScore(dblSkorAvg)
    .Query(fo2)
    .Explain() // <-- explain score computation for each hit
);

There is also a dedicated explain API to understand how a specific document's score is calculated.