eager « Fetch « JPA Q&A





1. JPA eager fetch does not join    stackoverflow.com

What exactly does JPA's fetch strategy control? I can't detect any difference between eager and lazy. In both cases JPA/Hibernate does not automatically join many-to-one relationships. Example: Person has a single address. ...

2. Can someone point me to a particularly good resource on JPA/Hibernate lazy/eager fetching?    stackoverflow.com

Looking for a really good article that includes strategies/bugs/workarounds. I would prefer a pure JPA solution but I know Hibernate offers a lot of extensions.

3. what is the difference between Hibernate.initialize and eager fetching    stackoverflow.com

Why I can't use EAGER fetching for the same purpose

4. What's the difference between lazy = false, eager and immediate fetching?    stackoverflow.com

I'm new on object persistence with Hibernate. I'm reading a book to try to understand what's the difference between lazy set to false, eager and immediate fetching but I don't see ...

5. Hibernate eager fetching    coderanch.com

I have a Player object that holds on to an address. When I retrieve the Player object from the database, it doesn't automatically retrieve the Address objects associated to it. What is the correct way to enable eager fetching for an object such that I don't have to do something like Player p = ... retrieve from database ... p.getAddress().getCity(); // ...

6. Hibernate:Eager fetching    coderanch.com

Hello all: I am trying to eager fetch a collection of objects. My hql is: select d.module from PermissionDefinition d left outer join fetch d.module where d.module.moduleId = 1 The above query throw the follwing error: "query specified join fetching, but the owner of the fetched association was not present in the select list" If I remove the "fetch" word, it ...

8. Hibernate 3 eager fetching    coderanch.com

Hi, in hibernate 3 I have object 1 that has eager relationship to object 2 and that one has eager relationship to object 3. My problem is that object 3 is lazily retrieved. AND even when I am doing a get on it it is still not retrieved from the db fully. Any ideas? Thanks.

9. Hibernate eager fetching issue    coderanch.com





10. EAGER fetching -- not working?!?    forum.hibernate.org

//retrieve data Customer cust = customerDao.findById(c1.getCustomerId()); Assert.assertNotNull(cust); for(CustomerPaymentHistory cph : cust.getPaymentHistory()){ System.out.println("\t" + cph ); ...

11. one-to-one eager fetch problem    forum.hibernate.org

Hi All, I have User and Department classes ,the relation from Department to User is one to one unidirectional(Department has head ,and User can be head of only one Department). and my problem is that i am not able to fetch users eagerly with the departments I tried using this mapping :

12. Force eager fetching for one particular query    forum.hibernate.org

13. Eager fetch n+1 problem    forum.hibernate.org

Hi, I have two classes Offer and Visibility. There is a 1-1 relation between Offer and visibility Code: Offer @OneToOne(optional = false, cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name = "FK_VisibilityID",nullable=false,updatable=false) @IndexedEmbedded public Visibility getVisibility() { return visibility; ...

14. Eager fetching for collections - beginer question    forum.hibernate.org

Hi I am new to hibernate and I am confused about fetching strategy. I have two tables with one-to-many relationship (e.g. Person and BankAccounts). According to hibernate reference I should use setFetchMode(FetchMode.JOIN) at runtime instead changing it in xml file. But why related collection is loaded only when I use an outer join? When I use inner join I have to ...

15. DOM4J createQuery not eagerly fetching    forum.hibernate.org

I have an entity which contains a OneToMany relationship, with eager fetching, with a second entity. This second entity has two OneToOne relationships, with eager fetching also, to a third and fourth class. The OneToOne relationships are unidirectional. I am calling createQuery() from a DOM4J session sending in "from entity" as the HQL. In the return I get the second entity ...

16. Lightweight Class and eager fetching    forum.hibernate.org

I have a class, let's say it's Cat, and this class has a many-to-one mapping to a class Owner. The Owner class is complex, so I created an OwnerSummary class, which Owner extends, such that I have lightweight and heavyweight versions. Cat has an OwnerSummary as an attribute. (Standard Lightweight Class implementation) The catch is this - I'd like to be ...





17. eager fetching help    forum.hibernate.org

Hy, I am a beginner in Hibernate and I have a problem. I have to tables, PERSON and CONTACT, in table person I have a person_id primary key, and in Contact I have a person_person_id foreign key which points to Person table. If I want to do an eager fetching I can use the following code: Session session = HibernateSession.currentSession(); List ...

18. Collection not initalized after eager fetch    forum.hibernate.org

// get parent without children List l = session.find("from Parent p left join fetch p.children where p.id=1"); Parent p = (Parent) l.get(0); assertTrue(Hibernate.isInitalized(p.getChildren()); // ok // Same query with Criteria List l = session.createCriteria(Parent.class).setFetchMode("children", FetchMode.EAGER).add( Expression.eq("id", new Integer(1)).list(); Parent p = (Parent) l.get(0); assertTrue(Hibernate.isInitalized(p.getChildren()); // fails if p has 0 children in db

19. eager fetch    forum.hibernate.org

I have a question regarding loading a graph of objects for return to the client. I have the following object graph obj A has a 1:1 with obj B obj A has a 1:n with obj C obj B has a 1:n with obj D obj B has a 1:n with obj E obj B has a m:n with obj F ...

20. Eager fetching and replication    forum.hibernate.org

Greetings! I'm currently need to replicate() subgraphs of objects from one DB to another. I'm searching for a way to effectively initialize a subgraph of objects (possibly proxied), containing multiple collections. Known solutions: 1) use lazy=false. Too poor performance in other cases... 2) Hibernate.initialize() recursivelty. Bad performance: causes n selects 3) eagerly fetch a graph in a single query usin criteria ...

21. eager fetching question    forum.hibernate.org

22. Eager fetch question    forum.hibernate.org

private void addEmailToPerson(Long personId, String emailAddress) { Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); Person aPerson = (Person) session.load(Person.class, personId); // The getEmailAddresses() might trigger a lazy load of the collection ...

23. Eager fetching settings ignored in HQL    forum.hibernate.org

I have chosen to write most of my queries using HQL. But I have now come to a point where I am doing performance tuning and I just discovered that when you write queries in HQL it ignores the fetch mode specified in your class mappings. I really don't understand the reasoning behind this. This creates a huge inconsistency issue. I ...

24. many-to-one EAGER fetching problem    forum.hibernate.org

25. Using eager fetching for certain queries    forum.hibernate.org

Hi, I want to query some data from the database, manipulate it a bit and display it. The problem is the objects are in persistent state after the query and hibernate starts trying to update the database (getting an exception because I set login rights to readonly). So I used transaction.commit() right after the query so hopefully the objects are in ...

26. Eager fetching of collections    forum.hibernate.org

Hello all: I am trying to eager fetch a collection of objects. My hql is: select d.module from PermissionDefinition d left outer join fetch d.module where d.module.moduleId = 1 The above query throw the follwing error: "query specified join fetching, but the owner of the fetched association was not present in the select list" If I remove the "fetch" word, it ...

27. Eager fetch is not done    forum.hibernate.org

Hi there, I have two classes: public class Edge implements Serializable { @Id @GenericGenerator(name = "gen", strategy = "uuid") @GeneratedValue(generator = "gen") private String id; @OneToMany(mappedBy="edge", fetch=FetchType.EAGER) @IndexColumn(name="id") private List lanes = new ArrayList(); public List getLanes() { return lanes; } public void setLanes(ArrayList lanes) { this.lanes = lanes; } } --------------------------- @Entity @Table(name="lanes") public class Lane implements Serializable { @Id ...

28. eager fetching data in hql    forum.hibernate.org

does anybody know how i can fetch only part of the information in hql in the following scenario: class A has a collection of class B. class A { Collection bees; } and i want to check an equality on the "bees" part. something like the following: ================ function: isEqual ------------------- A a1; A a2; if(a1.bees.size() != a2.bees.size()) return false; Iterator ...

29. Eager fetching problem    forum.hibernate.org

Hi, I have the following association: ... ... Looking at the log output there are two selects instead of one using a left outer join: select employee0_.employeeId as employeeId1_, employee0_.departmentId as departme2_1_, employee0_.lastname as lastname1_, employee0_.firstname as firstname1_, employee0_.employeeCode as employee5_1_ from Employee employee0_ where ...

30. Why eager fetch?    forum.hibernate.org

Dear Hibernate users, I have a conceptual question regarding the eager fetch. In the tutorial example, I noticed that within a session transaction, I can write either Person aPerson = (Person) session.load(Person.class, personId) or Person aPerson = (Person) session .createQuery("select p from Person p left join fetch p.events where p.id = :pid") .setParameter("pid", personId) .uniqueResult(); The later one is mentioned as ...

32. Fetch=join does not eager fetch collection    forum.hibernate.org

Hi I was following the examples in the 'Java Persistence and Hibernate' book with Hibernate 3.3.1 to try and load my collection upfront using fetch=join as follows: Code: ...