Hi,

I have a OneToMany relation between Foo and Bar.

class Foo {
@OneToMany(FetchType=Eager)
Set<Bar> bars;
}

The db mapping uses an extra join table.

When I do a "select * from Foo", I get for each row in Foo a join-select on bar and the join table.

Is it possible to optimize it in a way, that only a single select is used?

Thank you.

there are some posts on this in this forum.

what are the mappings for the Bar class? what is the sql generated once you issue "select b,f from Bar as b inner join b.foos as f"?

Could you be so kind to give me some links. Searching "onetomany join" leads to too many hits.

Foo in in Table FOO, Bar in Table BAR, the join table is FOO_BAR.
No further mappings, only the @OneToMany annotation with fetch=EAGER.

About the join: I have to try it.

One of mine :-)

* http://forum.hibernate.org/viewtopic.php?t=972526&highlight=

Try to search for:

"n+1 problem", "left join fetch" and also you me look into the manual http://www.hibernate.org/hib_docs/v3/reference/en/html/performance.html#performance-fetching

m.

Ah I see, a fetch join would do it.

I'm using JPA with Hibernate 3 as ORM.

Is the only way to use a fetch join a rewrite the JPA QL statement?
Or can I configure it somewhere (orm.xml)?

no JPA QL experience here (just learning), but general recommendation is (hibernate manual) -- use lazy fetching and enforce the eager fetching only selectively (when you need it).

in hbm.xml mapping files you can enforce the eager fetching using the fetch attribute.

also -- do some testing to be sure hibernate issues only the queries you think it does.