HQL to CriteriaQuery when using bitwise operators

Question

How do I convert this into a CriteraQuery:

select n
from TagRegistration t
join t.Tag n
where t.Status & :status > 0
order by count(t.ID) desc
       , n.Name asc

Answer 1

Here's how you could do it with the criteria API:

[Flags]
enum Bar{
   A = 0x01,
   B = 0x02,
   C = 0x04
}

var criteria = this.Session.CreateCriteria<Foo>()
            .Add( BitwiseFlags.IsSet( "Bar", Bar.A | Bar.C ) );

using:

public class BitwiseFlags : LogicalExpression
{
    private BitwiseFlags( string propertyName, object value, string op ) :
        base( new SimpleExpression( propertyName, value, op ),
        Expression.Sql( "?", value, NHibernateUtil.Enum( value.GetType() ) ) )
    {
    }

    protected override string Op
    {
        get { return "="; }
    }

    public static BitwiseFlags IsSet(string propertyName, Enum flags)
    {
        return new BitwiseFlags( propertyName, flags, " & " );
    }
}

should generate the following output where clause:

 FROM _TABLE
 WHERE  (this_.Bar & 5 = 5)

which should give you rows that have flags Bar.A and Bar.C set (excluding everything else). You should be able to use it with conjunction and disjunction too.

Answer 2

Did something like that a while ago.

Try something like this.

PropertyProjection projection = Projections.Property("t.ID");
PropertyProjection property = Projections.Property("n.Namn");
ICriteria criteria = session.CreateCriteria<TagRegistration>("t")
                .CreateCriteria("Tag","n")
                .Add(
                        Restrictions.Gt(
                            Projections.SqlProjection("({alias}.ID & 3) as bitWiseResult", new[] { "bitWiseResult" }, new IType[] { NHibernateUtil.Int32 })
                        , 0)
                     )
                .AddOrder(Order.Desc(Projections.Count(projection)))
                .AddOrder(Order.Asc(property))
                .SetProjection(Projections.GroupProperty(projection), Projections.GroupProperty(property))

Note this part {alias}.ID & 3) where I inserted the value directly which isn't very good but it works :)

You could do it better if you look at the test project of NHibernate Nhibernate/Criteria/AddNumberProjection.cs

But you need to do a subQuery to return fully initialized Tag I think this query is better to do in Hql.

Regards