Hashset add returns true instead of false

[Nazgaul]

Hi.
Kind hard to describe the scenario but ill do my best.
this is nhibernate v5.2.7 screenshot

this is nhibernate v5.3.2 screenshot

now _followers is a hashset of followers
if i do a foreach before i do the add it return false as expected.
On 5.3.2 i don't see any select to bring the collection...

the mapping in user is

  HasMany(x => x.Followers).Access.CamelCaseField(Prefix.Underscore)
                .Cascade.AllDeleteOrphan()
                .KeyColumn("UserId").Inverse().AsSet();

and

       HasMany(x => x.Following).KeyColumn("FollowerId")
                .Cascade.AllDeleteOrphan().AsSet();

again this is hard scenario due to complex domain module.
I can give you any more info that you'd like.

[maca88]

Can you provide the id mapping of Follow class? Does Follow class override Equals and GetHashCode methods, if it does, could you provide how they are implemented?

[Nazgaul]

public FollowMap()
{
    Id(x => x.Id).GeneratedBy.GuidComb();
    References(x => x.User).Column("UserId").Not.Nullable().UniqueKey("c_follower");
    References(x => x.Follower).Column("FollowerId").Not.Nullable().UniqueKey("c_follower");
    Map(x => x.Created).Insert().Not.Update();
    Map(x => x.Subscriber).Nullable();
    Table("UsersRelationship");
}

Follow implementation of equal methods

public virtual bool Equals(Follow other)
{
    if (ReferenceEquals(null, other)) return false;
    if (ReferenceEquals(this, other)) return true;
    return Equals(User.Id, other.User.Id) && Equals(Follower.Id, other.Follower.Id);
}

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

public override int GetHashCode()
{
    return (User.Id.GetHashCode() * 101) ^ (Follower.Id.GetHashCode() * 107);
}

I go from one entity ( course) and then go to course.tutor.user.addFollwer(user)
And if i do a foreach before ( to bring the collection ) the hashset is working ( and i see a select is generated).
on 5.3 - the select is not generated.

[maca88]

As I expected, the problem here is that Follow class uses Id property as the identifier but the overridden Equals and GetHashCode use User and Follower instead. This scenario will not work with lazy="extra" even with 5.2.x, because the element existence check performed on the database would check the Id property which in this case is set to a default value. The reason why in version 5.2.x works with lazy="true" and not in 5.3.x, is because the optimization done in #2010 to avoid initializing the collection in case a transient element is added to the collection. I made a fix in #2481, which fallbacks to the previous behavior in case the element overrides Equals method.

[Nazgaul]

Thanks allot of identifying the problem

[fredericDelaporte]

Fixed with #2481