NHibernate - Saving simple parent-child relationship generates unnecessary selects with assigned id
- by Alice
Entities:
public class Parent
{
virtual public long Id { get; set; }
virtual public string Description { get; set; }
virtual public ICollection<Child> Children { get; set; }
}
public class Child
{
virtual public long Id { get; set; }
virtual public string Description { get; set; }
virtual public Parent Parent { get; set; }
}
Mappings:
public class ParentMap : ClassMap<Parent>
{
public ParentMap()
{
Id(x => x.Id).GeneratedBy.Assigned();
Map(x => x.Description);
HasMany(x => x.Children)
.AsSet()
.Inverse()
.Cascade.AllDeleteOrphan();
}
}
public class ChildMap : ClassMap<Child>
{
public ChildMap()
{
Id(x => x.Id).GeneratedBy.Assigned();
Map(x => x.Description);
References(x => x.Parent)
.Not.Nullable()
.Cascade.All();
}
}
and
using (var session = sessionFactory.OpenSession())
using (var transaction = session.BeginTransaction())
{
var parent = new Parent { Id = 1 };
parent.Children = new HashSet<Child>();
var child1 = new Child { Id = 2, Parent = parent };
var child2 = new Child { Id = 3, Parent = parent };
parent.Children.Add(child1);
parent.Children.Add(child2);
session.Save(parent);
transaction.Commit();
}
this codes generates following sql
NHibernate: SELECT child_.Id, child_.Description as Descript2_0_, child_.Parent_id as Parent3_0_ FROM [Child] child_ WHERE child_.Id=@p0;@p0 = 2 [Type: Int64 (0)]
NHibernate: SELECT child_.Id, child_.Description as Descript2_0_, child_.Parent_id as Parent3_0_ FROM [Child] child_ WHERE child_.Id=@p0;@p0 = 3 [Type: Int64 (0)]
NHibernate: INSERT INTO [Parent] (Description, Id) VALUES (@p0, @p1);@p0 = NULL[Type: String (4000)], @p1 = 1 [Type: Int64 (0)]
NHibernate: INSERT INTO [Child] (Description, Parent_id, Id) VALUES (@p0, @p1, @p2);@p0 = NULL [Type: String (4000)], @p1 = 1 [Type: Int64 (0)], @p2 = 2 [Type:Int64 (0)]
NHibernate: INSERT INTO [Child] (Description, Parent_id, Id) VALUES (@p0, @p1, @p2);@p0 = NULL [Type: String (4000)], @p1 = 1 [Type: Int64 (0)], @p2 = 3 [Type:Int64 (0)]
Why are these two selects generated and how can I remove it?
