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