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Re: [eclipselink-users] Order of persist operations

Hi Tom, 

here is a more specific test case: 

@Entity @Table(name="ROLE")
class Role {

    @Id @Column(name="ID", length=20, nullable=false)
    String id

    @Column(name="PARENT_ID", length=20, nullable=true)
    String parentId

    @Column(name="NAME", length=255, nullable=false)
    String name

    @ManyToOne
    @JoinColumn( name="PARENT_ID", referencedColumnName="ID", updatable=false, insertable=false)
    RoleType parentRole
    
}

I have created a tool that imports data from XML file. In this case the XML would look like: 

<data>
    <Role  id="MAIN" name="Main Role" />
    <Role  id="USER" name="User"  parent_id="MAIN"/>
    <Role id="ADMINISTRATOR" name="Administrator" parent_id="MAIN" />
</data>

The MAIN role has NULL in PARENT_ID. The rest of the records have MAIN as a parent role. 
The order of the insert statements is vital for the successful import of the data. 

I have implemented a XML parser that creates new entities and persists them in the order they are coming from the XML file. 

HOWEVER

Hibernate inserts the data in the correct order - e.g. MAIN, USER, ADMINISTRATOR. 

EclipseLink however would execute the insert statements in a random order every time, e.g.  USER, MAIN, ... which causes a FK error. 

Flushing the session on each persist is not a solution. 

EclipseLink needs to execute the database statements in the same order as the persist() and merge() calls. 

Regards, 
Deyan 



On Jan 17, 2013, at 15:00 , Tom Ware <tom.ware@xxxxxxxxxx> wrote:

Can you provide a specific test-case where the order actually causes a problem?

The JPA specification allows a persistence provider to order statements in the way that is most efficient for it.  This, in fact, is essential to solving the very problem you are worried about.  i.e. A JPA provider has to be able to compute an order of statements that allow foreign key constraints to be properly satisfied.  As long as your entities are configured so that JPA is made aware of all your constraints, the order of statements should not cause any problems of that type.

The power of this functionality is that when you are writing your JPA code, you do not have to think about the database constraints, you just manipulate your objects and the order will be taken care of.

-Tom

On 17/01/2013 6:27 AM, Deyan Tsvetanov wrote:
> Well, the order that EclipseLink chooses is RANDOM :)
> It is a fairly simple example, only 1 entity with only 1 column.
> I'd really expect that the INSERT statements are executed in same order as the
> persist() calls.
> 
> My real-life use case is importing data from an XML file into the database.
> There are relations and FKs in my database and when exported and re-imported the
> order of the XML entries, persist() calls and INSERT statements is critical.
> EclipseLink basically inserts each XML entry randomly. Currently the only
> workaround is to flush after each persist call. It could work for few hundred
> calls,
> but not for few thousand.
> 
> JPA says nothing about the order of the database operations. When writing the
> spec they probably have assumed that it would be logical to execute the database
> operations in the
> same order as the persist() or merge() calls.
> This is not the case of mixed remove(), persist() and merge() calls, in our case
> we have only persist() calls and the case is very simple.
> 
> Best regards,
> Deyan
> 
> 
> On Jan 17, 2013, at 13:19 , Wim Bervoets <wbervoets@xxxxxxxxx
> <mailto:wbervoets@xxxxxxxxx>> wrote:
> 
> If you want to know the order in which the rows were inserted I use @OrderColumn
> (eg. in combinantion with INDEX(..) function in a JPQL for example).
> 
> I think that EclipseLink can choose the order in which it commits the entities
> to the database... (I haven't read the JPA spec so this is an assumption)
> 
> Wim
> 
> 
> On Thu, Jan 17, 2013 at 12:09 PM, Deyan Tsvetanov <deyan@xxxxxxxxxxxx
> <mailto:deyan@xxxxxxxxxxxx>> wrote:
> 
>    Hibernate persists the entities in the correct order:
> 
>    2:57:58,867 TRACE TypeFactory:72 - Scoping types to session factory
>    org.hibernate.internal.SessionFactoryImpl@395fa2b5
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,365 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST0
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,369 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST1
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,371 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST2
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,372 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST3
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,373 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST4
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,375 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST5
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,376 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST6
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,377 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST7
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,378 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST8
>    Hibernate: insert into ROLE (ID) values (?)
>    12:57:59,380 TRACE BasicBinder:83 - binding parameter [1] as [VARCHAR] - TEST9
> 
> 
> 
>    On Jan 17, 2013, at 12:19 , Deyan Tsvetanov <deyan@xxxxxxxxxxxx
>    <mailto:deyan@xxxxxxxxxxxx>> wrote:
> 
>    Hi guys,
> 
>    I am experiencing a weird imho behaviour of Eclipselink and I'd really like
>    to hear some other opinions .
> 
>    I have a pretty simple entity with assigned IDs;
> 
>    @Entity@Table(name="ROLE")
>    public class Role implements Serializable {
> 
>    privatestaticfinallongserialVersionUID= 1L;
> 
>    @Id @Column(name="ID", length=20, nullable=false)
>    public String id;
> 
> 
>    }
> 
> 
>    I am executing the following operations:
> 
>    public static void main(String[] args) {
>    EntityManagerFactory emf =
>    Persistence.createEntityManagerFactory("EclipseLinkJPATest");
> 
>    EntityManager em = emf.createEntityManager();
> 
>    em.getTransaction().begin();
>    for (int i = 0; i < 10; i++) {
>    Role r = new Role();
>    r.id = "TEST" + i;
>    em.persist(r);
>    }
>    em.getTransaction().commit();
> 
>    em.close();
>    emf.close();
>    }
> 
>    And I'd expect that the INSERT queries will be executed in the same order as
>    the persist() method is called:
>    TEST0, TEST1, TEST2 , etc.
> 
>    But in the real life the insert queries are in a random order every time:
> 
>    EL Fine]: sql: 2013-01-17
>    12:13:58.11--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST1]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.113--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST6]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.114--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST2]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.115--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST7]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.117--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST4]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.121--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST8]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.123--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST3]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.124--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST9]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.126--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST5]
>    [EL Fine]: sql: 2013-01-17
>    12:13:58.127--ClientSession(1694665796)--Connection(1795160456)--INSERT INTO
>    ROLE (ID) VALUES (?)
>    bind => [TEST0]
> 
>    As you can see the order if insert queries is:
>    TEST1, TEST6, TEST2, TEST7, TEST4, etc.
> 
> 
>    That is really weird and wrong ! :)
>    I dug a lot and could not find a solution.
> 
>    Please help :)
> 
>    Thanks in advance,
>    Deyan
> 
> 
> 
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