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From "David Wisneski" <>
Subject Re: extraneous joins OPENJPA-134
Date Fri, 16 Feb 2007 21:43:58 GMT
When both sides of a relationhship are EAGER this should result in
only one join (not two).

Account <-> Holidng is  One Account has Many holdings. Both roles of
the relationship are marked EAGER.

If I join
   Account t0 join Holding t1 on(t1.account=t0.accountId)
there should not be a need to do
   Account t0 join Holding t1 on(t1.account=t0.accountId)  join
Account t2 on(t2.accountid=t1.account)

t2 would be the same values as t0.   Putting in the extraneous join is
not needed and we see performance degradation compared to other OR
products (e.g.  Hibernate).

I think we can just not generate the extra join -- unless someone sees
something that I don't see.

On 2/15/07, catalina shaw <> wrote:
> Regardless the ManyToOne is EAGER by default, when its
> inverse relationship if
> 1. set to EAGER  (select a from a a;  a has the OneToManyRelation property)
> or
> 2. set to LAZY but Eagerly Fetched by query (select ... from a a join fetch
> a.OneToManyRelation )
> We see unneeded joins being generated.
> The issue is why generating the extraneous joins that can be optimized away.
> >> I've looked at the code and it looks correct to me and tried various
> >> things like making the inverse LAZY. But it always generating the
> >> extraneous join. I've attached the entity source code.
> >>
> >> The relationship causing problem is
> >>
> >> @ManyToOne
> >> @JoinColumn(name="ACCOUNT_ACCOUNTID")
> >> private Accountejb2 account2;
> >ManyToOne is eager by default, so right now both sides are eager.

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