Version of unchanged entity is updated only because collection is dirty

[perahoky]

Hello,

we have entities with (ISet-) collections which are updated when nothing has changed, only the collection is dirty.

Short:
NHibernate executes the following SQL:
"update Entity set RowVersion = 2 where Id = ... ; "
which seems useless since the entity / row is unchanged, but only a collection has changed.

I've created an example project.
NHibernateExample.UnchangedEntityUpdated

I'm using FluentNHibernate for this example.
The following is pseudocode.

Assume we have an entity:

class Entity
{
  Public Guid Id { get; set; }
  public int RowVersion { get; set; }
  public Entity Parent { get; set; }
  public ISet<Entity> Children { get; set; }
}

With the following map

class EntityMap : Classmap<Entity>
{
  public EntityMap()
  {
    this.Id(x => x.Id).Not.Nullable().GeneratedBy.Assigned;
    this.Version(x => x.RowVersion).Not.Nullable().UnsavedValue("0");
    this.HasMany(x => x.Children).Inverse(); // our children are responsible for saving themselves ... 
    this.References(x => x.Parent).Foreignkey("Parent_Id");
  }
}

We create our first data (with a fresh session which is committed and flushed at the end etc)

Guid parentId = Guid.NewGuid();
Guid childId= Guid.NewGuid();

// session 1
{
  using ISession session = OpenSession();
  // session.BeginTransaction(ReadCommitted);
  var parent = new Entity() { Id = parentId };

  session.SaveOrUpdate(parent);
  // transaction.Commit()
  session.Flush();
}

In some other session we create our child data and assign parent:

// session 2
{
  using ISession session = OpenSession();

  var child= new Entity();
  var parent = session.Get<Entity>(parentId);

  parent.Children.Add(child); // just as example
  child.Parent = parent;

  session.SaveOrUpdate(parent, child);
  session.Flush();
}

Current behavior:
Nhibernate generates SQL which is updating the entities RowVersion and nothing else.

  update "Entity" set "RowVersion"=2 where "Id" = parentId;
  insert into "Entity" (Id, RowVersion) values (childId, 1);

Expected behavior:
"parent" (identified by "parentId") remains unchanged (RowVersion 1) since it was not changed.

  insert into Entity (Id, RowVersion) values (childId, 1);

Test:

// session 3
{
  using ISession session = OpenSession();

  var child = session.Get<Entity>(childId);
  var parent = session.Get<Entity>(parentId);

  Assert.AreEqual(1, parent.RowVersion);
  Assert.AreEqual(1, child.RowVersion);
}

Can i change / Is it possible to change behavior to "Only udpate RowVersion when some persistent Property has changed"?

Thank you,
Best regards,

[bahusoid]

From docs :

You may disable NHibernate's automatic version increment for particular properties and collections by setting the optimistic-lock mapping attribute to false. NHibernate will then no longer increment versions if the property is dirty.

In Fluent NHibernate you need to add .Not.OptimisticLock() to collection mappings:

this.HasMany(x => x.Children).Inverse().Not.OptimisticLock();

[perahoky]

Hi,

thank you very much and have a nice day / weekend. :)
We've searched but used the wrong keywords despite its this easy ...