[FIXED] Get document scores within Hibernate Search

Issue

we query multiple indices but with different field names and merge the result into a global search. To add pagination, I want to use the scores by sorting the results by score and calculate the page myself.

My question is now: How to I get the score for each document? I saw that I can sort by score but not how the get the actual score value.

Any help is apreciated!

P.S. I'm using an Elasticsearch backend and hibernate search 6.1.5

Solution

It's in the documentation: score projection.

List<Float> hits = searchSession.search( Book.class )
        .select( f -> f.score() )
        .where( f -> f.match().field( "title" )
                .matching( "robot dawn" ) )
        .fetchHits( 20 );

And if you want the entity and the score, use both the score projection and the entity projection, and combine them with a composite projection.

List<MyPair<Book, Float>> hits = searchSession.search( Book.class )
        .select( f -> f.composite( 
                MyPair::new, 
                f.entity(), 
                f.score() 
        ) )
        .where( f -> f.matchAll() )
        .fetchHits( 20 ); 

Note that Hibernate Search 6.2 (still in development) will introduce a slightly more explicit syntax:

List<MyPair<Book, Float>> hits = searchSession.search( Book.class )
        .select( f -> f.composite()
                .from( f.entity(), f.score() )
                .as( MyPair::new ) )
        .where( f -> f.matchAll() )
        .fetchHits( 20 ); 

Answered By - yrodiere
Answer Checked By - Clifford M. (JavaFixing Volunteer)