Hello,
I'm using NHibernate 1.2.0 beta3.

I have 2 simples objects linked by a One-To-Many collection with the following mapping :
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="WindowsApplication1" assembly="WindowsApplication1">
<class name="Account" table="Account" select-before-update="true" dynamic-update="true">
<id name="Id">
<column name="AccountId" sql-type="char(32)" not-null="true"/>
<generator class="uuid.hex" />
</id>
<version name="Version"/>
<property name="NoCli" />
<property name="NoDos" />
<set name="Roles" lazy="false" cascade="all-delete-orphan" inverse="true">
<key column="AccountId" />
<one-to-many class="Role"/>
</set>
</class>
<class name="Role" table="Role" select-before-update="true" dynamic-update="true">
<id name="Id">
<column name="RoleId" sql-type="char(32)" not-null="true"/>
<generator class="uuid.hex" />
</id>
<version name="Version"/>
<property name="Property1" />
<property name="Property2" />
<many-to-one name="Account" column="AccountId" not-null="true"/>
</class>
</hibernate-mapping>


I instanciate and bind a list of Account using the folling commands :
ISession session = m_sessionFactory.OpenSession();
IQuery query = session.CreateQuery("select c from Account as c");
m_list = new BindingList<Account>(query.List<Account>());
bindingSource1.DataSource = m_list;
session.Close();

Then, I save my list of Account using the folling commands :
ISession session = m_sessionFactory.OpenSession();
ITransaction tx = session.BeginTransaction();
try
{
foreach (Account account in m_list)
{
session.SaveOrUpdate(account);
}
tx.Commit();
}
catch
{
tx.Rollback();
throw;
}
session.Close();

I have 3 questions :

First question, if I update a property of one of the object, when I save my list many times, it keeps sending the same SQL UPDATE order and incrementing each time the version of the corresponding object. I was expecting to have an update only the first time I save the list.

Second question, when I save the list, it send an SQL SELECT order for each object (Account and Role) in my list. I understand that NHibernate needs to read what is the current state in the database to decide if it's necessary or not to perform an update. Is it possible to use the Second Level cache instead of reading the database to know what is the current state ? I tried by adding the element <cache usage="read-write"/> in my mapping but it didn't change anything...

Third question, when I delete a role, and then save my list, Nhibernate knows that it need to generate a DELETE SQL order. How can it guess it ? It is not by reading the database... It is not by using the session... Is it because of the use of these special collections that implements ISet ?

Thanks for your help...

I did not received an answer to any of my 3 little questions...
Are they stupid questions ?

#1 - It is incrementing because you are issuing a save with the most current version number and are refreshing the object. If someone were to pull in the object with the same version number after you have already loaded the object and then you save your object, then their save would fail because they have an older version (is that pessimistic ?)
#2 - Make sure you have set up the 2nd level cache in the config and that you are using the right strategy...I believe read-write strategy will hit the DB in this scenario.
#3 - You are using cascade strategy all-delete-orphan for your collection, so when the Role is deleted NHibernate will issue a DELETE for the Role if it isn't in another collection. Read the docs about 'cascade' strategy.

Good luck
MIKE

BTW: Don't forget you can use the using statement on the transaction part:



Just makes the code a little more concise,

HTH a little :-)