I've read in Hibernate docs that using inverse="true" on the one side of many-to-many relationship and inverse="false" on the other prevents from inserting two identical rows to relationship table. I've wrote a test application just to get on with it and, to my surprise, I got two inserts instead one. Could anybody explain this? Thnx in advance...

Association mappings are as follows:

<set name="applications" inverse="true" table="hb_application_developers">
<key column="developer_id"/>
<many-to-many column="application_id" class="pl.test.ApplicationHb"/>
</set>

on the one side and:

<set name="developers" inverse="false" table="hb_application_developers">
<key column="application_id"/>
<many-to-many column="developer_id" class="pl.test.DeveloperHb"/>
</set>

on the other. The code does above:

Session session = HibernateUtil.getSession(); //obtains session from SessionFactory
Transaction tx = session.beginTransaction();

ApplicationHb application = new ApplicationHb("XyberMech");
DeveloperHb developer = new DeveloperHb("A.Solecki");

session.save(application);
session.save(developer);

session.flush();

application.getDevelopers().add(developer);
developer.getApplications().add(application);

session.update(application);

HibernateUtil.closeSession(session, tx);//commits transaction and closes session

And the result SQL is:

select nextval ('hibernate_sequence')
select nextval ('hibernate_sequence')
insert into hb_application (title, id) values ('XyberMech', 546555)
insert into hb_developer (name, id) values ('A.Solecki', 546556)
insert into hb_application_developers (application_id, developer_id) values (546555, 546556)
insert into hb_application_developers (developer_id, application_id) values (546556, 546555)

On the other hand, when I set both sides to inverse=false or both sides to inverse="true", everything works fine o_O.
I use Hibernate 3.0 and Postgres 7.4 .

I had to have a total eclipse of my mind when I was writing previous post. Everything works fine now, with inverse="true" on one side and inverse="false" on the other.

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Theory: When nothing works, but you know what's wrong
Practice: When everything works fine, but you have no idea why
I mix those two approaches: Nothing works and I have no idea why