Fluent NHibernate Unidirectional relationships causing many updates

Question

I have done some search on StackOverflow and google in general and I am still having trouble finding out why this is happening and how to fix it. I am new to NHibernate and FluentNHibernate, so please be gentle :)

While doing some intergration tests, I found that if I was to just modify the Seller's Name, NHibernate would generate update scripts for all the Contacts and the Login as well, and delete all the reference in Contact_Seller and readd them.

I feel like I should do something like Inverse() in my maps, but I do not know how since Contact and Login do not have references to Sellers or Buyers in my object model.

Here is my setup (Objects, Maps, and Database). Let me know if you need more info, and thanks.

class Buyer{
    public int BuyerID {get;set;}
    public Login Login {get;set;}
    public IList<Contact> Contacts  {get;set;}
    ... Other Buyer properties ...

}
class Seller{
    public int SellerID {get;set;}  
    public Login Login {get;set;}
    public IList<Contact> Contacts  {get;set;}
    public string Name {get;set;}
    ... Other Seller properties ...
}
class Login{
    public int LoginID {get;set;}
    public string Username {get;set;}
    public byte[] Password {get;set;}
    public string Email {get;set;}
}
class Contact{
    public int ContactID {get;set;}
    ... Contact Info...
}

public BuyerMap()
{    
    Id(x => x.BuyerID);

    ... Other Seller properties ...

    HasManyToMany(x => x.Contacts).Table("Contact_Buyer").Cascade.All();            
    References(x => x.Login).Cascade.All();

}

public SellerMap()
{    
    Id(x => x.SellerID);

    ... Other Seller properties ...

    HasManyToMany(x => x.Contacts).Table("Contact_Seller").Cascade.All();           
    References(x => x.Login).Cascade.All();

}
public LoginMap()
    {
        Id(x => x.LoginID);

        Map(x => x.Username);
        Map(x => x.Password);
        Map(x => x.Email);

    }

public ContactMap()
{
    Id(x => x.ContactID);

        ... Other Contact properties ...        

}

TABLE Buyer(
    [BuyerID] [int] IDENTITY(1,1) NOT NULL, 
    [LoginID] [int] NULL,
    ... Other Buyer fields ...
    )


TABLE Seller(
    [SellerID] [int] IDENTITY(1,1) NOT NULL,    
    [LoginID] [int] NOT NULL,
    [Name]     [varchar] NOT NULL,
    ... Other Seller fields ...
    )

TABLE Login(
    [LoginID] [int] IDENTITY(1,1) NOT NULL,     
    ... Other Login fields ...
    )

TABLE Contact(
    [ContactID] [int] IDENTITY(1,1) NOT NULL,   
    ... Other Contact fields ...
    )

TABLE Contact_Seller(
    [ContactID] [int] NOT NULL, 
    [SellerID]  [int] NOT NULL, 
    )

TABLE Contact_Buyer(
    [ContactID] [int] NOT NULL, 
    [BuyerID]  [int] NOT NULL,  
    )

Answer 1

looking at the mappings you are not interested in the Order of Contacts but i assume they should be unique. So change the Contacts collection to ICollection<Contact> and

HasManyToMany(x => x.Contacts).AsSet();

the NHibernate can optimise some access since it knows that the link table contains unique pairs.