如何在自定义查询中加载@ElementCollection？

Question

I want to reduce the amount of querys run by spring. When getting an object with @ElementCollection via SQL I want to get the data for the ElementCollections directly via a JOIN within the quers.

The attribute with the ElementCollection

@ElementCollection(fetch = FetchType.EAGER)
    @JoinTable(name = "song_genre_list")
    @org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    private List<String> genre;

The Method that uses a custom string:

@Query(
    value = "select distinct s.*, g.* from musicdb.songs s left join musicdb.song_genre_list g on s.id = g.song_id where s.name like ?1 or s.artist like ?1",
    nativeQuery = true)
List<Song> searchSong(String title);

How I would imagine defining a query that also loads this element collection:

SELECT DISTINCT s.*, g.* FROM musicdb.songs s LEFT JOIN musicdb.song_genre_list g ON s.id = g.song_id WHERE s.name LIKE ?1 OR s.artist LIKE ?1

What Spring currently does (loading the genres for 3 songs with more querys):

Hibernate: select distinct s.*, g.* from musicdb.songs s left join musicdb.song_genre_list g on s.id = g.song_id where s.name like ?1 or s.artist like ?1
Hibernate: select genre0_.song_id as song_id1_4_0_, genre0_.genre as genre2_4_0_ from musicdb.song_genre_list genre0_ where genre0_.song_id=?
Hibernate: select genre0_.song_id as song_id1_4_0_, genre0_.genre as genre2_4_0_ from musicdb.song_genre_list genre0_ where genre0_.song_id=?
Hibernate: select genre0_.song_id as song_id1_4_0_, genre0_.genre as genre2_4_0_ from musicdb.song_genre_list genre0_ where genre0_.song_id=?

What I want Spring to do:

Hibernate: select distinct s.*, g.* from musicdb.songs s left join musicdb.song_genre_list g on s.id = g.song_id where s.name like ?1 or s.artist like ?1

The required Data for the ElementCollection is already included with the join. How can I tell spring to import that Data?

Answer 1

FetchType.EAGER will already load the genres for you, so you dont need to write a join in your original query. But for that hibernate hibernate uses separate queries by default. To change this add the annotation '@Fetch(FetchMode.JOIN)' on the genre field