NHibernate insert/update problem

Fob.hbm.xml

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true">
  <class xmlns="urn:nhibernate-mapping-2.2" name="ValueMapping.Fob, ValueMapping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="`Fob`">
    <id type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="id" />
      <generator class="native" />
    </id>
    <property name="Something" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="Something" />
    </property>
  </class>
</hibernate-mapping>

Foo.hbm.xml

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true">
  <class xmlns="urn:nhibernate-mapping-2.2" name="ValueMapping.Foo, ValueMapping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="`Foo`">
    <id type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="id" />
      <generator class="native" />
    </id>
    <property name="Name" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="Name" />
    </property>
    <set name="Aliases">
      <key>
        <column name="Foo_id" />
      </key>
      <element type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <column name="name" />
      </element>
    </set>
    <set cascade="all-delete-orphan" name="Bars">
      <key>
        <column name="Foo_id" />
      </key>
      <composite-element class="ValueMapping.Bar, ValueMapping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
        <property name="Rate" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
          <column name="Rate" />
        </property>
        <property name="Value" type="System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
          <column name="Value" />
        </property>
      </composite-element>
    </set>
    <set cascade="all-delete-orphan" name="Fobs">
      <key>
        <column name="Foo_id" />
      </key>
      <one-to-many class="ValueMapping.Fob, ValueMapping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
    </set>
  </class>
</hibernate-mapping>

output.sql

-- statement #1
INSERT INTO [Foo]
           (Name)
VALUES     ('bob' /* @p0 */)
select SCOPE_IDENTITY()

-- statement #2
INSERT INTO [Fob]
           (Something)
VALUES     ('You are standing in an open field west of a big white house' /* @p0 */)
select SCOPE_IDENTITY()

-- statement #3
INSERT INTO [Fob]
           (Something)
VALUES     ('It is very dark, you are likely to be eaten by a Grue' /* @p0 */)
select SCOPE_IDENTITY()

-- statement #4
INSERT INTO [Fob]
           (Something)
VALUES     ('You were eaten by a Grue' /* @p0 */)
select SCOPE_IDENTITY()

-- statement #5
UPDATE [Fob]
SET    Foo_id = 1 /* @p0 */
WHERE  id = 1 /* @p1 */

-- statement #6
UPDATE [Fob]
SET    Foo_id = 1 /* @p0 */
WHERE  id = 2 /* @p1 */

-- statement #7
UPDATE [Fob]
SET    Foo_id = 1 /* @p0 */
WHERE  id = 3 /* @p1 */

source.cs

using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;
using FluentNHibernate.Mapping;
using NHibernate.Tool.hbm2ddl;

namespace ValueMapping
{
    public class Program
    {
        private static void Main(string[] args)
        {
            HibernatingRhinos.Profiler.Appender.NHibernate.NHibernateProfiler.Initialize();

            if (Directory.Exists("schema"))
                Directory.Delete("schema", true);
            Directory.CreateDirectory("schema");

            var cfg =
                Fluently.Configure()
                    .Database(
                    MsSqlConfiguration.MsSql2005
                        .ConnectionString(x => x.Server(".").Database("sandbox").TrustedConnection())
                        .ProxyFactoryFactory<NHibernate.ByteCode.LinFu.ProxyFactoryFactory>()
                    )
                    .Mappings(x =>
                              x.FluentMappings
                                  .Add<FooMapping>()
                                  .Add<FobMapping>()
                                  .ExportTo("schema"))
                    .BuildConfiguration();

            new SchemaExport(cfg).Drop(false, true);
            new SchemaExport(cfg).Execute(false, true, false);

            var sf = cfg.BuildSessionFactory();

            object id;

            using (var session = sf.OpenSession())
            using (var t = session.BeginTransaction())
            {
                var f = new Foo();
                f.Name = "bob";
                //f.Aliases.Add("fred");
                //f.Aliases.Add("mary");

                //f.Bars.Add(new Bar {Rate = 5, Value = 10});
                //f.Bars.Add(new Bar {Rate = 20, Value = 3});

                f.Fobs.Add(new Fob {Something = "You are standing in an open field west of a big white house"});
                f.Fobs.Add(new Fob {Something = "It is very dark, you are likely to be eaten by a Grue"});
                f.Fobs.Add(new Fob {Something = "You were eaten by a Grue"});

                id = session.Save(f);

                t.Commit();
            }

            using (var session = sf.OpenSession())
            using (var t = session.BeginTransaction())
            {
                var f = session.Get<Foo>(id);

                //f.Aliases.Remove("fred");
                //f.Bars.Remove(new Bar {Rate = 20, Value = 3});
                f.Fobs.Remove(f.Fobs.First());

                t.Commit();
            }

            HibernatingRhinos.Profiler.Appender.NHibernate.NHibernateProfiler.Stop();
            Thread.Sleep(1000);
        }
    }

    public class Foo
    {
        public Foo()
        {
            Aliases = new HashSet<string>();
            Bars = new HashSet<Bar>();
            Fobs = new HashSet<Fob>();
        }

        public virtual string Name { get; set; }
        public virtual ICollection<string> Aliases { get; set; }
        public virtual ICollection<Bar> Bars { get; set; }
        public virtual ICollection<Fob> Fobs { get; set; }
    }

    public class Bar
    {
        public virtual int Value { get; set; }
        public virtual int Rate { get; set; }

        public bool Equals(Bar other)
        {
            if (ReferenceEquals(null, other)) return false;
            if (ReferenceEquals(this, other)) return true;
            return other.Value == Value;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            if (ReferenceEquals(this, obj)) return true;
            if (obj.GetType() != typeof (Bar)) return false;
            return Equals((Bar) obj);
        }

        public override int GetHashCode()
        {
            return Value;
        }
    }

    public class Fob
    {
        public virtual string Something { get; set; }
    }

    public sealed class FooMapping : ClassMap<Foo>
    {
        public FooMapping()
        {
            Id<int>("id").GeneratedBy.Native();
            Map(x => x.Name);

            HasMany(x => x.Aliases).AsSet().Element("name");
            HasMany(x => x.Bars)
                .AsSet()
                .Cascade.AllDeleteOrphan()
                .Component(
                c =>
                    {
                        c.Map(x => x.Rate);
                        c.Map(x => x.Value);
                    }
                );
            HasMany(x => x.Fobs).AsSet().Cascade.AllDeleteOrphan();
        }
    }

    public sealed class FobMapping : ClassMap<Fob>
    {
        public FobMapping()
        {
            Id<int>("id").GeneratedBy.Native();
            Map(x => x.Something);
        }
    }
}