Is it possible for Hibernate to fetch two levels of sets with one select?

Question

I have three entities:

@Entity
@Table(name="a")
class A {

  @Id
  Long id;

  @OneToMany(fetch = FetchType.EAGER)
  @JoinColumn(name = "a_id")    
  Set<B> bs;

  // ... other fields
}

@Entity
@Table(name = "b")
class B {

  @Id
  Long id;

  @OneToMany(fetch = FetchType.EAGER)
  @JoinColumn(name = "c_id")
  Set<C> cs;

  // ... other fields
}

@Entity
@Table(name = "c")
class C {

  @Id
  Long id;

  // ... other fields
}

When I use Criteria API from JPA to get given A, Hibernate first fetches just A, then for each A, all B's and finally for each B all C's.

Is it possible to force fetching with one select which is in theory possible?

score 2 · Accepted Answer · edited May 23 '17 at 12:22

2

Hibernate doesn't support well fetching multiple eager collections. Take a look here.

Btw do you really need those collection as eagerly loaded?

Hibernate cannot simultaneously fetch multiple bags

edited May 23 '17 at 12:22

Community

1
1

answered Mar 18 '13 at 16:05

Łukasz Rzeszotarski

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It doesn't really matter what kind of fetching I choose. It's instantly converted into another object graph to keep in memory. – Patryk Dobrowolski Mar 19 '13 at 09:41
I tried another approach and fetch using C as a root. But seems it doesn't work any faster. Probably because fetching is costly itself, and that's because of CLOB fields here, I bet. I'll leave it as it is and change fetching to LAZY. Need to live with this. – Patryk Dobrowolski Mar 19 '13 at 09:44

score 0 · Answer 2 · answered Mar 18 '13 at 16:00

0

Sounds like not possible without internal iteration.

In such cases i would like to suggest Hibernate Native Sql query.

answered Mar 18 '13 at 16:00

Suresh Atta

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Is it possible for Hibernate to fetch two levels of sets with one select?

2 Answers2