Question

i’m using oracle with FluentNHibernate automapping with alterations & NHibernate
the problem is how to specify the constraint name by overriding the mapping model??

the generated sql like this:

alter table FirstTable
    add constraint FK_VerLongIdentifierLongerThan30Characther
    foreign key (FirstTableID) 
    references SecondTable;

i need to change the “FK_VerLongIdentifierLongerThan30Characther” to smaller identifier by overriding the mapping model like this:

model.Override<SomeClass>(m =>
    {
        m.HasOne<SomeOtherClass>(c => c.SomeProperty).?????????;
        //or
        m.????????
    }
  )

Answer 1

Instead of doing an override for each class with this problem, what I have done is create a mapping convention which would truncate objects with surpass a 30-character naming scheme on foreign keys, has many and many to many relations:

---

public class OracleIHasManyConvention : IHasManyConvention
{
    public void Apply(IOneToManyCollectionInstance instance)
    {
        var keyName = string.Format(CultureInfo.InvariantCulture, "FK_{0}_{1}",
                                    instance.Member.Name,
                                    instance.EntityType.Name).Truncate(30);

        instance.Key.ForeignKey(keyName);
    }
}

---

public class OracleForeignKeyConvention : FluentNHibernate.Conventions.ForeignKeyConvention
{
    protected override string GetKeyName(Member property, System.Type type)
    {
        var name = property == null
                   ? "Id_" + type.Name.ToUnderscoredNaming()
                   : "Id_" + property.Name.ToUnderscoredNaming();

        return name.Truncate(30);
    }
}

---

Then I would call these conventions like this:

var cfg = Fluently.Configure()
                .Database(SQLiteConfiguration.Standard.UsingFile("foobar.lite3"))
                .Mappings(m => m.AutoMappings.Add(AutoMap.AssemblyOf<Product>()
                                                      .Where(a => a.Namespace == typeof (Product).Namespace)
                                                      .Conventions.Add<OracleIHasManyConvention>()
                                                      .Conventions.Add<OracleForeignKeyConvention>()
                                                      .Conventions.Add<OracleGeneralConvention>()
                                                      .Conventions.Add<CascadeAllConvention>()
                                   ));

---

Here’s the Truncate extension:

public static class StringHelper
{
    public static string Truncate(this string text, int endIndex)
    {
        if (text.Length > endIndex)
        {
            text = text.Substring(0, endIndex).TrimEnd('_');
        }
        return text;
    }
}

I hope this is useful in any way. 🙂