NH-3178 - Exception when using one-to-one properties in a criteria projections

[nhibernate-bot]

Nathan Baulch created an issue — 6th June 2012, 15:58:59:

I get the following exception when using a one-to-one property in a criteria projection:

NHibernate.Exceptions.GenericADOException: could not execute query

[ SELECT this_.USERID as y0_ FROM USER this_ ]
[SQL: SELECT this_.USERID as y0_ FROM USER this_] ---> System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at NHibernate.Loader.Criteria.CriteriaLoader.GetResultColumnOrRow(Object[] row, IResultTransformer customResultTransformer, IDataReader rs, ISessionImplementor session) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Criteria\CriteriaLoader.cs:line 101
   at NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode<] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[> keys, Boolean returnProxies) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Loader.cs:line 360
   at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Loader.cs:line 468
   at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Loader.cs:line 246
   at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Loader.cs:line 1590
   --- End of inner exception stack trace ---
   at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) in d:\GitHub\nhibernate\nhibernate-core\src\NHibernate\Loader\Loader.cs:line 1599

Using many-to-one projections on the other hand does work. The difference seems to be the AbstractType.GetColumnSpan method which returns a hard coded zero in the OneToManyType override and a non-zero value in the ManyToOneType override.

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Alexander Zaytsev added a comment — 6th June 2012, 16:44:57:

Nathan Baulch, could you please provide an example or test case?

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Nathan Baulch added a comment — 6th June 2012, 17:29:28:

The NH unit test project is a little overwhelming but I'm able to reproduce the issue by adding the following test to the MergeFixture class. I doubt this is an appropriate place for such a test to live permanently, I just needed a convenient place to use the one-to-one Person.Detail property.

<Test>
public void OneToOneProjection()
{
    using (var s = OpenSession())
    {
        var p = new Person {Name = "steve"};
        new PersonalDetails {SomePersonalDetail = "I have big feet", Person = p};
        s.Save(p);
        s.Flush();
        s.CreateCriteria<Person>().SetProjection(Projections.Property("Details")).List();
    }
}

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Alexander Zaytsev added a comment — 7th June 2012, 11:29:47:

Nathan Baulch, it just not supported, see Oskar's explanation on NH-3176

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Oskar Berggren added a comment — 8th June 2012, 6:55:10:

NH-3176 was about collections. one-to-one sounds more natural to support, technically there shouldn't be much difference from many-to-one. It might be a feature request rather then a bug though.

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Nathan Baulch added a comment — 11th June 2012, 7:22:50:

My thoughts exactly Oskar, and if it can't be supported for technical reasons then a more meaningful error would be nice.