Hibernate search querying in MYSQL DB

Hibernate Search
1

Query is running on hibernate search and its giving proper response but while constructing response in spring boot application , its querying in the mysql DB as well, how to avoid this ? one thing i understood is using projections but any simple way to avoid this.

2

If you don’t want the data of matching documents to be extracted from the database, then indeed, use projections:

SearchSession searchSession = Search.session( entityManager );

List<String> result = searchSession.search( Book.class ) 
        .select( f -> f.field( "title", String.class ) ) 
        .where( f -> f.matchAll() )
        .fetchHits( 20 );

This won’t hit the database at all.

In Hibernate Search 6.2, there’s a more convenient, annotation-based projection definition:

@ProjectionConstructor 
public record MyBookProjection(String title, 
        List<MyBookProjection.Author> authors) { 
    @ProjectionConstructor 
    public record Author(String firstName, String lastName) {
    }
}

SearchSession searchSession = Search.session( entityManager );

List<MyBookProjection> hits = searchSession.search( Book.class )
        .select( MyBookProjection.class )
        .where( f -> f.matchAll() )
        .fetchHits( 20 );

It is, however, still in Alpha and currently has limitations, such as being limited to indexed fields and not supporting ID/score projections.

3

In this case any ideal way to add fields into select dynamically, For example fields to be sent as response should be dynamic instead of manually adding like this –

Search.session(entityManager).search(ProductOrderEntity.class)
.extension(ElasticsearchExtension.get())
.select(f → f.composite(f.field(“directorName”, String.class),
f.field(“movies.title”, String.class).multi()))
.where(f → f.fromJson(json)).fetch(offset, limit);

4

If you mean “dynamically based on request parameters”, that’ll probably be easier using the object-based syntax instead of the lambda-based syntax:

SearchSession searchSession = Search.session( entityManager );

SearchScope<Book> scope = searchSession.scope( Book.class );

SearchProjectionFactory<?, ?> f = scope.projection();
SearchProjection<?> projection;
if ( some condition ) {
     projection = f.field( "directorName", String.class ).toProjection();
}
else {
    projection = f.composite(
                f.field("directorName"),
                f.field("movies.title").multi()
             ).toProjection();
}

List<?> result = searchSession.search( scope )
        .select( projection )
        .where( scope.predicate().matchAll().toPredicate() )
        .fetchHits( 20 );

If you mean “dynamically for each document”, then no, that’s not possible. You’ll have to do that using post-processing.