Re: [eclipselink-users] JPA:how to avoid join table for ManyToOne

[Tom Ware <tom.ware@xxxxxxxxxx>]

I suggest creating a read-only Basic mapping on A for b's id and querying on 
that column instead.

Something like:

SELECT o from A o where o.b_id = 1

Zarar Siddiqi wrote:
> Instead of the @JoinTable use @JoinColumn(name="b").
>
>
>
> On Tue, Apr 21, 2009 at 1:44 PM,  <cn.thesky@xxxxxxxxx> wrote:
> > hello all,
> >
> >    for example
> >
> >   @Entity
> >   class A {
> >      @Id
> >      long a_id;
> >
> >     String a_name;
> >
> >      @ManyToOne
> >      @JoinTable(name="b_id")
> >      B b;
> >  }
> >
> >
> > @Entity
> > class B {
> >    @Id
> >    int b_id ;
> >
> >    String b_name;
> >
> > }
> >
> > jpa query:
> >     SELECT o from A o where o.b.id = 1
> >
> >
> > I hope the generated sql like:
> >    select a_id,a_name from A where b = 1;
> >
> > but the eclipselink generated the following sql
> >
> >   select t0.a_id,t0.a_name from A t0, B t1 where t0.b = t1.b_id AND t1.b_id
> > = 1
> >
> >
> > This is, my table A is very very large table , maybe more than 40m rows;
> > table B is small, 1,000 - 10,000rows. I can't afford  the performance lost
> > due to any join operation for table A .
> >  Any suggestion except native sql?  I hope all place like this should not
> > use join table, for the sake of performance.
> >
> > thanks
> >
> >
> > _______________________________________________
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> > eclipselink-users@xxxxxxxxxxx
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