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From "catalina wei" <catalina....@gmail.com>
Subject Re: Trouble understanding JOINs
Date Wed, 12 Dec 2007 20:28:13 GMT
This a bug  related to OPENJPA-135. That issue reported that OpenJPA
implementation not conforming to JPA spec where duplicate is expected but
OpenJPA is not

returning duplicates (for JOIN FETCH queries without DISTINCT keyword).

By SELECT *DISTINCT *.. JOIN Fetch, it is supposed to eliminate duplicates
while OpenJPA is doing exactly the opposite (not eliminating the
duplicates).

I will look into OPENJPA-135 (meanwhile as been assigned to me by Kevin
Sutter) as soon as I have a chance to work on it.
Catalina
On 11/29/07, plinskey@gmail.com <plinskey@gmail.com> wrote:
>
> Hi Jacek,
>
> Based on that description, it sounds like a bug in OpenJPA's list
> handling somewhere.
>
> Do the SQL statements issued differ?
>
> -Patrick
>
> On 11/28/07, Jacek Laskowski <jacek@laskowski.net.pl> wrote:
> > Hi,
> >
> > I've got two entities: Osoba (Whole) and Konto (Part) in OneToMany
> > association. Each contains id and name attributes. I decided to test
> > inner and left fetch joins.
> >
> > I created 2 Osoba's, but only one got 2 Konto's.
> >
> > When I run
> >
> > SELECT o FROM Osoba o
> >
> > it returns 2 entities which is fine. However, when I run
> >
> > SELECT o FROM Osoba o JOIN FETCH o.konta
> >
> > it returns 1 entity which is still fine but the number of Konta
> > entities is...4 (!).
> >
> > When I changed the type of Osoba.konta (plural of konto in Polish)
> > from List<Konto> to Set<Konto> the above query returned 2 which was
> > what I had first expected.
> >
> > Could anyone explain it to me? I seem to be missing some SQL classes
> > on how joins are supposed to work so any pointers to documentation
> > would be fine too.
> >
> > Here the entities go (with Set<Konto>):
> >
> > package pl.jaceklaskowski.jpa;
> >
> > import java.io.Serializable;
> > import java.util.HashSet;
> > import java.util.Set;
> > import javax.persistence.CascadeType;
> > import javax.persistence.Entity;
> > import javax.persistence.GeneratedValue;
> > import javax.persistence.GenerationType;
> > import javax.persistence.Id;
> > import javax.persistence.NamedQueries;
> > import javax.persistence.NamedQuery;
> > import javax.persistence.OneToMany;
> >
> > @Entity
> > @NamedQueries({
> >     @NamedQuery(name = "Osoba.poImieniu", query = "SELECT o FROM Osoba
> > o WHERE o.imie = :imie"),
> >     @NamedQuery(name = "Osoba.wszystkieOsoby", query = "SELECT o FROM
> Osoba
> > o"),
> >     @NamedQuery(name = "Osoba.wszystkieOsoby.JOIN_FETCH", query =
> > "SELECT o FROM Osoba o JOIN FETCH o.konta"),
> >     @NamedQuery(name = "Osoba.wszystkieOsoby.LEFT_JOIN_FETCH", query =
> > "SELECT o FROM Osoba o LEFT JOIN FETCH o.konta")
> > })
> > public class Osoba implements Serializable {
> >
> >     private static final long serialVersionUID = 1L;
> >     private int id;
> >     private String imie;
> >     private Set<Konto> konta = new HashSet<Konto>();
> >
> >     protected Osoba() {
> >     }
> >
> >     public Osoba(String imie) {
> >         this.imie = imie;
> >     }
> >
> >     @Id
> >     @GeneratedValue(strategy = GenerationType.AUTO)
> >     public int getId() {
> >         return id;
> >     }
> >
> >     public void setId(int id) {
> >         this.id = id;
> >     }
> >
> >     @OneToMany(cascade=CascadeType.PERSIST)
> >     public Set<Konto> getKonta() {
> >         return konta;
> >     }
> >
> >     public void setKonta(Set<Konto> konta) {
> >         this.konta = konta;
> >     }
> >
> >     public void addKonto(Konto konto) {
> >         getKonta().add(konto);
> >     }
> >
> >     public String getImie() {
> >         return imie;
> >     }
> >
> >     public void setImie(String imie) {
> >         this.imie = imie;
> >     }
> >
> >     @Override
> >     public String toString() {
> >         return "Osoba[id=" + getId() + "]";
> >     }
> > }
> >
> > package pl.jaceklaskowski.jpa;
> >
> > import java.io.Serializable;
> > import javax.persistence.Entity;
> > import javax.persistence.GeneratedValue;
> > import javax.persistence.GenerationType;
> > import javax.persistence.Id;
> >
> > @Entity
> > public class Konto implements Serializable {
> >
> >     private static final long serialVersionUID = 1L;
> >     private int id;
> >     private String numer;
> >
> >     protected Konto() {
> >     }
> >
> >     public Konto(String numer) {
> >         this.numer = numer;
> >     }
> >
> >     @Id
> >     @GeneratedValue(strategy = GenerationType.AUTO)
> >     public int getId() {
> >         return id;
> >     }
> >
> >     public void setId(int id) {
> >         this.id = id;
> >     }
> >
> >     public String getNumer() {
> >         return numer;
> >     }
> >
> >     public void setNumer(String numer) {
> >         this.numer = numer;
> >     }
> >
> >     @Override
> >     public String toString() {
> >         return "Konto[id=" + getId() + "]";
> >     }
> > }
> >
> > Jacek
> >
> > --
> > Jacek Laskowski
> > http://www.JacekLaskowski.pl
> >
>
>
> --
> Patrick Linskey
> 202 669 5907
>

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