Hibernate OneToMany bi-directional relation is slow

Question

I have Sessions and Users classes with following bi-directional OneToManymapping(generated with hibernate reverse engineering tool):

public class Users {
    @OneToMany(fetch=FetchType.LAZY, mappedBy="users")
    public Set<Sessions> getSessionses() {
        return this.sessionses;
    }
}

public class Sessions {
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="USER_ID")
    public Users getUsers() {
        return this.users;
    }
}

And here is my code which creates new session for user:

Session s = ...;
Users user = (Users) s.createCriteria(Users.class)
             ./*restrictions...*/.uniqueResult();
Sessions userSession = new Sessions();
userSession.setUsers(user);
s.save(userSession);
user.getSessionses().add(userSession); // here getSessionses() has 2k records

User has 2k sessions and therefore last line is very slow.

How can I link session with user without fetching whole sessions collection ?

Do you really need the collection to be a Set? When you add an element into it, hibernate needs to load the elements to check for duplicates — Guillaume, May 15 '13 at 09:56
@Guillaume Set is rather the mandate data-structure imposed by Hibernate to maintain the uniqueness — sanbhat, May 15 '13 at 10:03
When you have unique ids your results are results are unique anyway. But with a list you could speed the process up. — Lukas Eichler, May 15 '13 at 10:08
This might be a duplicate of this: http://stackoverflow.com/questions/1409523/hibernate-how-to-persist-a-new-item-in-a-collection-without-loading-the-entire — Balázs Németh, May 15 '13 at 10:12

score 4 · Accepted Answer · answered May 15 '13 at 10:29

4

Have a look at Hibernate's extra-lazy loading feature. You enable that by annotating your collection with @LazyCollection(LazyCollectionOption.EXTRA). There is this example to look at, and there's Set used in this one.

public class Users {
    @OneToMany(fetch=FetchType.LAZY, mappedBy="users")
    @LazyCollection(LazyCollectionOption.EXTRA)
    public Set<Sessions> getSessionses() {
        return this.sessionses;
    }
}

answered May 15 '13 at 10:29

Balázs Németh

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Great, thanks! It works perfectly. In this case hibernate generates only single query: `SELECT 1 FROM SESSIONS WHERE USER_ID=? and SESSION_ID=?`. It's the only solution, which helps to fix issue without having to change Set to List. – Oleksandr.Bezhan May 15 '13 at 12:03

score 1 · Answer 2 · answered May 15 '13 at 10:17

1

I'm not certain if hibernate would add this connection both ways but instead of adding a Session to a User set the User of a Session. This way you don't have to load every session.

answered May 15 '13 at 10:17

Lukas Eichler

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Hibernate [doc](http://docs.jboss.org/hibernate/core/3.3/reference/en/html/tutorial.html#tutorial-associations-usingbidir) says, that: `"setting the link on both sides" is absolutely necessary with bi-directional links`. Therefore it's required to set link on both sides. – Oleksandr.Bezhan May 15 '13 at 10:25
Can you refute my comment with any official documentation proof link ? – Oleksandr.Bezhan May 15 '13 at 12:22

Hibernate OneToMany bi-directional relation is slow

2 Answers2